UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 10-K

CNA FINANCIAL CORPORATION

(Exact name of registrant as specified in its charter)

(312) 822-5000

(Registrant's telephone number, including area code)

Securities registered pursuant to Section 12(g) of the Act:

None

Indicate by check mark if the registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act. Yes [x] No [ ]

Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or Section 15(d) of the Act. Yes [ ] No [x]

Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. Yes [x] No [ ]

Indicate by check mark whether the registrant has submitted electronically and posted on its corporate Web site, if any, every Interactive Data File required to be submitted and posted pursuant to Rule 405 of Regulation S-T (§232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit and post such files). Yes [x] No [ ]

Indicate by check mark if disclosure of delinquent filers pursuant to Item 405 of Regulation S-K (§229.405 of this chapter) is not contained herein, and will not be contained, to the best of registrant's knowledge, in definitive proxy or information statements incorporated by reference in Part III of this Form 10-K or any amendment to this Form 10-K. [x]

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Act). Yes [ ] No [x]

As of February 10, 2017, 270,621,4009, 2018, 271,217,644 shares of common stock were outstanding. The aggregate market value of the common stock held by non-affiliates of the registrant as of June 30, 20162017 was approximately $844$1,362 million based on the closing price of $31.42$48.75 per share of the common stock on the New York Stock Exchange on June 30, 2016.2017.

PART I

ITEM 1. BUSINESS

Our insurance products primarily include commercial property and casualty coverages, including surety. Our services include warranty, risk management information services warranty and claims administration. Our products and services are primarily marketed through independent agents, brokers and managing general underwriters to a wide variety of customers, including small, medium and large businesses, insurance companies, associations, professionals and other groups.

Competition

The property and casualty insurance industry is highly competitive both as to rate and service. We compete with a large number of stock and mutual insurance companies and other entities for both distributors and customers. Insurers compete on the basis of factors including products, price, services, ratings and financial strength. Accordingly, we must continuously allocate resources to refine and improve our insurance products and services.

Regulation

The insurance industry is subject to comprehensive and detailed regulation and supervision. Regulatory oversight by applicable agencies is exercised through review of submitted filings and information, examinations (both financial and market conduct), direct inquiries and interviews. Each domestic and foreign jurisdiction has established supervisory agencies with broad administrative powers relative to licensing insurers and agents, approving policy forms, establishing reserve requirements, prescribing the form and content of statutory financial reports and regulating capital adequacy and the type, quality and amount of investments permitted. Such regulatory powers also extend to governance requirements, risk assessment practices and disclosures and premium rate regulations which require thatrequiring rates not be excessive, inadequate or unfairly discriminatory, governance requirements and risk assessment practice and disclosure.discriminatory. In addition to regulation of dividends by insurance subsidiaries, intercompany transfers of assets may be subject to prior notice or approval by insurance regulators, depending on the size of such transfers and payments in relation to the financial position of the insurance subsidiaries making the transfer or payment.

Domestic insurers are also required by state insurance regulators to provide coverage to certain insureds who would not otherwise be considered eligible by the insurers. Each state dictates the types of insurance and the level of coverage that must be provided to such involuntary risks. Our share of these involuntary risks is mandatory and generally a function of our respective share of the voluntary market by line of insurance in each state.

Further, domestic insurance companies are subject to state guaranty fund and other insurance-related assessments. Guaranty funds are governed by state insurance guaranty associations which levy assessments to meet the funding needs of insolvent insurer estates. Other insurance-related assessments are generally levied by state agencies to fund various organizations, including disaster relief funds, rating bureaus, insurance departments and workers'

compensation second injury funds, or by industry organizations that assist in the statistical analysis and ratemaking process, and we have the ability to recoup certain of these assessments from policyholders.

As our insurance operations are conducted in a multitude of both domestic and foreign jurisdictions, we are subject to a number of regulatory agency requirements applicable to a portion, or all, of our operations. These include among other things,but are not limited to, the State of Illinois Department of Insurance (which is our global group-wide supervisor), the U.K. Prudential Regulatory Authority and Financial Conduct Authority, the Bermuda Monetary Authority and the Office of Superintendent of Financial Institutions in Canada.

Hardy, a specialized Lloyd's of London (Lloyd's) underwriter, is also supervised by the Council of Lloyd's, which is the franchisor for all Lloyd's operations. The Council of Lloyd's has wide discretionary powers to regulate Lloyd's underwriting, such as establishing the capital requirements for syndicate participation. In addition, the annual business plans of each syndicate are subject to the review and approval of the Lloyd's Franchise Board, which is responsible for business planning and monitoring for all syndicates.

Capital adequacy and risk management regulations, referred to as Solvency II, apply to our European operations and are enacted by the European Union'sCommission, the executive body of the European Commission.Union (E.U.). Additionally, the International Association of Insurance Supervisors (IAIS) continues to consider regulatory proposals addressing group supervision, capital requirements and enterprise risk management. The U.S. Federal Reserve, the U.S. Federal Insurance Office and the National Association of Insurance Commissioners (NAIC) are working with other global regulators to define such proposals. It is not currently clear to what extent the IAIS activities will impact the Companyaffect us, as any final proposal would ultimately need to be legislated or regulated by each individual country or state.

Although the U.S. federal government does not currently directly regulate the business of insurance, federal legislative and regulatory initiatives can impactaffect the insurance industry. These initiatives and legislation include proposals relating to potential federal oversight of certain insurers; terrorism and natural catastrophe exposures; cybersecurity risk management; federal financial services reforms; and certain tax reforms.

The Terrorism Risk Insurance Program Reauthorization Act of 2015 provides for a federal government backstop for insured terrorism risks through 2020. The mitigating effect of such law is part of the analysis of our overall risk posture for terrorism and, accordingly, our risk positioning may change if such law were modified.

We also continue to invest in the security network of our systems on an enterprise-wide basis, especially considering the implications of data and privacy breaches. This requires an investment of a significant amount of resources by us on an ongoing basis. Potential implications of possible cybersecurity legislation on such current investment, if any, are uncertain.

The foregoing laws and proposals, either separately or in the aggregate, create a regulatory and legal environment that may require changes in our business plan or significant investment of resources in order to operate in an effective and compliant manner.

Additionally, various legislative and regulatory efforts to reform the tort liability system have, and will continue to, impactaffect our industry. Although there has been some tort reform with positive impact to the insurance industry, new causes of action and theories of damages continue to be proposed in court actions and by federal and state legislatures that continue to expand liability for insurers and their policyholders.

Employee Relations

Direct Written Premiums by Geographic Concentration

Set forth below is the distribution of our direct written premiums by geographic concentration.

Approximately 7.9%7.7%, 8.0%7.9% and 8.8%8.0% of our direct written premiums were derived from outside of the United States for the years ended December 31, 2017, 2016 2015 and 2014.2015.

Available Information

ITEM 1A. RISK FACTORS

Our business faces many risks and uncertainties. These risks and uncertainties could lead to events or circumstances that have a material adverse effect on our results of operations, equity, business and insurer financial strength and corporate debt ratings. We have described below the most significant risks facing us. There may be additional risks that we do not yet know of or that we do not currently perceive to be as significant that may also impactaffect our business. You should carefully consider and evaluate all of the information included in this report and any subsequent reports we may file with the SEC or make available to the public before investing in any securities we issue.

If we determine that our recorded insurance reserves are insufficient to cover our estimated ultimate unpaid liability for claim and claim adjustment expenses, we may need to increase our insurance reserves which would result in a charge to our earnings.

We maintain insurance reserves to cover our estimated ultimate unpaid liability for claim and claim adjustment expenses, including the estimated cost of the claims adjudication process, for reported and unreported claims. Insurance reserves are not an exact calculation of liability but instead are complex management estimates developed utilizing a variety of actuarial reserve estimation techniques as of a given reporting date. The reserve estimation process involves a high degree of judgment and variability and is subject to a number of factors which are highly uncertain. These variables can be affected by both changes in internal processes and external events. Key variables include claimsclaim severity, frequency of claims, mortality, morbidity, discount rates, inflation, claimsclaim handling policies and procedures, case reserving approach, underwriting and pricing policies, changes in the legal and regulatory environment and the lag time between the occurrence of an insured event and the time of its ultimate settlement. Mortality is the relative incidence of death. Morbidity is the frequency and severity of injury, illness, sickness and diseases contracted.

There is generally a higher degree of variability in estimating required reserves for long-tail coverages, such as general liability and workers' compensation, as they require a relatively longer period of time for claims to be reported and settled. The impact of changes in inflation and medical costs are also more pronounced for long-tail coverages due to the longer settlement period.

We are subject to the uncertain effects of emerging or potential claims and coverage issues that arise as industry practices and legal, judicial, social, economic and other environmental conditions change. These issues have had, and may continue to have, a negative effect on our business by either extending coverage beyond the original underwriting intent or by increasing the number or size of claims, resulting in further increases in our reserves. The effects of unforeseen emerging claim and coverage issues are extremely difficult to predict.

Emerging or potential claimsclaim and coverage issues include, but are not limited to, uncertainty in future medical costs in workers' compensation. In particular, medical cost inflation could be greater than expected due to new treatments, drugs and devices; increased healthcare utilization; and/or the future costs of healthcare facilities. In addition, the relationship between workers' compensation and government and private healthcare providers could change, potentially shifting costs to workers' compensation.

In light of the many uncertainties associated with establishing the estimates and making the judgments necessary to establish reserve levels, we continually review and change our reserve estimates in a regular and ongoing process as experience develops from the actual reporting and settlement of claims and as the legal, regulatory and economic environment evolves. If our recorded reserves are insufficient for any reason, the required increase in reserves would be recorded as a charge against our earnings in the period in which reserves are determined to be insufficient. These charges could be substantial.

Our actual experience could vary from the key assumptions used to determine active life reserves for long term care policies.

Our active life reserves for long term care policies are based on our best estimate assumptions as of December 31, 2015, due to an unlocking at that date. Key assumptions include morbidity, persistency (the percentage of policies remaining in force), discount rate and future premium rate increases. These assumptions, which are critical bases for our reserve estimates, are inherently uncertain. If actual experience varies from these assumptions or the future outlook for these assumptions changes, we may be required to increase our reserves. See the Life & Group Non-

Core Policyholder Reserves portion of Reserves - Estimates and Uncertainties section of MD&A in Item 7 for more information.

Estimating future experience for long term care policies is highly uncertain, because the required projection period is very long and there is limited historical and industry data available to us, as only a small portion of the long term care policies which have been written to date are in claims paying status. Morbidity and persistency trends, inclusive of mortality, can be volatile and may be negatively affected by many factors including, but not limited to, policyholder behavior, judicial decisions regarding policy terms, socioeconomic factors, cost of care inflation, changes in health trends and advances in medical care.

A prolonged period during which interest rates remain at levels lower than those anticipated in our reserving would result in shortfalls in investment income on assets supporting our obligations under long term care policies, which may require changes to our reserves. This risk is more significant for our long term care products because the long potential duration of the policy obligations exceeds the duration of the supporting investment assets. Further, changes to the corporate tax code may also impactaffect the rate at which we discount our reserves. In addition, we may not receive regulatory approval for the level of premium rate increases we request. Any adverse deviation between the level of future premium rate increases approved and the level included in our reserving assumptions may require an increase to our reserves.

If our estimated reserves are insufficient for any reason, including changes in assumptions, the required increase in reserves would be recorded as a charge against our earnings in the period in which reserves are determined to be insufficient. These charges could be substantial.

Catastrophe and systemic losses are unpredictable and could result in material losses.

Catastrophe losses are an inevitable part of our business. Various events can cause catastrophe losses. These events can be natural or man-made, and may include hurricanes, windstorms, earthquakes, hail, severe winter weather, fires, floods, riots, strikes, civil commotion, cyber attacks, pandemics and acts of terrorism. The frequency and severity of these catastrophe events are inherently unpredictable. In addition, longer-term natural catastrophe trends may be changing and new types of catastrophe losses may be developing due to climate change, a phenomenon that has been associated with extreme weather events linked to rising temperatures and includes effects on global weather patterns, greenhouse gases, sea, land and air temperatures, sea levels, rain, hail and snow.

The extent of our losses from catastrophes is a function of the total amount of our insured exposures in the affected areas, the frequency and severity of the events themselves, the level of reinsurance assumed and ceded, reinsurance reinstatement premiums and state residual market assessments, if any. It can take a long time for the ultimate cost of any catastrophe losses to us to be finally determined, as a multitude of factors contribute to such costs, including evaluation of general liability and pollution exposures, infrastructure disruption, business interruption and reinsurance collectibility. Reinsurance coverage for terrorism events is provided only in limited circumstances, especially in regard to “unconventional” terrorism acts, such as nuclear, biological, chemical or radiological attacks. As a result of the items discussed above, catastrophe losses are particularly difficult to estimate. Additionally, catastrophic events could cause us to exhaust our available reinsurance limits and could adversely affect the cost and availability of reinsurance.

Additionally, claimClaim frequency and severity for some lines of business can be correlated to an external factor such as economic activity, financial market volatility, increasing health care costs or changes in the legal or regulatory environment. Claim frequency and severity can also be correlated to insureds' use of common business practices, equipment, vendors or software. This can result in multiple insured losses emanating out of the same underlying cause. In these instances, we may be subject to increased claim frequency and severity across multiple policies or lines of business concurrently. While we do not define such instancessystemic losses as catastrophes for financial reporting purposes, they are similar to catastrophes in terms of the uncertainty and potential impact on our results.

We have exposures related to asbestos and environmental pollution (A&EP) claims, which could result in material losses.

Our property and casualty insurance subsidiaries have exposures related to A&EP claims. Our experience has been that establishing claim and claim adjustment expense reserves for casualty coverages relating to A&EP claims is subject to uncertainties that are greater than those presented by other claims. Additionally, traditional actuarial

methods and techniques employed to estimate the ultimate cost of claims for more traditional property and casualty exposures are less precise in estimating claim and claim adjustment expense reserves for A&EP. As a result,

We use analytical models to assist our decision making in key areas such as pricing, reserving and capital modeling and may be adversely affected if actual results differ materially from the model outputs and related analyses.

We use various modeling techniques and data analytics (e.g., scenarios, predictive, stochastic and/or forecasting) to analyze and estimate exposures, loss trends and other risks associated with our assets and liabilities. This includes both proprietary and third party modeled outputs and related analyses to assist us in decision-making related to underwriting, pricing, capital allocation, reserving, investing, reinsurance and catastrophe risk, among other things. We incorporate numerous assumptions and forecasts about the future level and variability of policyholder behavior, loss frequency and severity, interest rates, equity markets, inflation, capital requirements, and currency exchange rates, among others. The modeled outputs and related analyses from both proprietary and third parties are subject to various assumptions, uncertainties, model design errors and the inherent limitations of any statistical analysis, including those arising from the use of historical internal and industry data and assumptions.

In addition, the effectiveness of any model can be degraded by operational risks including, but not limited to, the improper use of the model, including input errors, data errors and human error. As a result, actual results may differ materially from our modeled results. The profitability and financial condition of the Company substantially depends on the extent to which our actual experience is consistent with assumptions we use in our models and ultimate model outputs. If, based upon these models or other factors, we misprice our products or fail to appropriately estimate the risks we are exposed to, our business, financial condition, results of operations or liquidity may be adversely affected.

We face intense competition in our industry; we may be adversely affected by the cyclical nature of the property and casualty business and the evolving landscape of our distribution network, as well as the availability and cost of reinsurance.network.

All aspects of the insurance industry are highly competitive and we must continuously allocate resources to refine and improve our insurance products and services to remain competitive. We compete with a large number of stock and mutual insurance companies and other entities, some of which may be larger or have greater financial or other resources than we do, for both distributors and customers. This includes agents and brokers who may increasingly compete with us to the extent that markets continue to provide them with direct access to providers of capital seeking exposure to insurance risk. Insurers compete on the basis of many factors, including products, price, services, ratings and financial strength. The competitor insurer landscape has evolved substantially in recent years, with significant consolidation and new market entrants, resulting in increased pressures on our ability to remain competitive, particularly in implementing pricing that is both attractive to our customer base and risk-appropriate to the Company.us.

We market our insurance products worldwide primarily through independent insurance agents and insurance brokers, who also promote and distribute the products of our competitors. Any change in our relationships with our distribution network agents and brokers, including as a result of consolidation and their increased promotion

We may be adversely affected by technological changes or disruptions in the insurance marketplace.

In addition, agents and brokers, technology companies, or other third parties may create alternate distribution channels for commercial business that may adversely impact product differentiation and pricing. For example, they may create a digitally enabled distribution channel that may adversely impact our competitive position. Our efforts or the efforts of agents and brokers with respect to new products or alternate distribution channels, as well as changes in the way agents and brokers utilize greater levels of data and technology, could adversely impact our business relationship with independent agents and brokers who currently market our products, resulting in a lower volume and/or profitability of business generated from these sources.

We may not be able to obtain sufficient reinsurance at a cost we deem acceptable, which could result in increased exposure to risk or a decrease in our underwriting commitments.

We may not be able to collect amounts owed to us by reinsurers, which could result in higher net incurred losses.

We have significant amounts recoverable from reinsurers which are reported as receivables on our Consolidated Balance Sheets and are estimated in a manner consistent with claim and claim adjustment expense reserves or future policy benefitsbenefit reserves. The ceding of insurance does not, however, discharge our primary liability for claims. As a result, we are subject to credit risk relating to our ability to recover amounts due from reinsurers. Certain of our reinsurance carriers have experienced credit downgrades by rating agencies within the term of our contractual relationship, which indicates an increase in the likelihood that we will not be able to recover amounts due. In addition, reinsurers could dispute amounts which we believe are due to us. If the amounts due from reinsurers that we are able to collect are less than the amount recorded by us with respect to such amounts due, our net incurred losses will be higher.

A portion of our business is written under deductible policies. Under these policies, we are obligated to pay the related insurance claims and are reimbursed by the policyholder to the extent of the deductible, which may be significant.

Moreover, certain policyholders purchase retrospectively rated workers' compensation policies (i.e., policies in which premiums are adjusted after the policy period based on the actual loss experience of the policyholder during the policy period). Retrospectively rated policies expose us to additional credit risk to the extent that the adjusted premium is greater than the original premium, which may be significant. As a result, we are exposed to policyholder

credit risk. If the amounts due from policyholders that we are able to collect are less than the amounts recorded with respect to such amounts due, our incurred losses will be higher.

We may incur significant realized and unrealized investment losses and volatility in net investment income arising from changes in the financial markets.

Our investment portfolio is exposed to various risks, such as interest rate, credit spread, issuer default, equity prices and foreign currency, which are unpredictable. Financial markets are highly sensitive to changes in economic

We have significant holdings in fixed maturityincome investments that are sensitive to changes in interest rates. A decline in interest rates may reduce the returns earned on new fixed maturityincome investments, thereby reducing our net investment income, while an increase in interest rates may reduce the value of our existing fixed maturityincome investments. The value of our fixed maturityincome investments is also subject to risk that certain investments may default or become impaired due to deterioration in the financial condition of issuers of the investments we hold or in the underlying collateral of the security. Any such impairments which we deem to be other-than-temporary would result in a charge to our earnings.

In addition, we invest a portion of our assets in equity securities and limited partnerships which are subject to greater market volatility than our fixed maturityincome investments. Limited partnership investments generally provide a lower level of liquidity than fixed maturity or equity investments which may also limit our ability to withdraw assets.

Further, we hold a portfolio of commercial mortgage loans. We are subject to credit risk relatingrelated to our ability to recover amounts duethe recoverability of loan balances, which is influenced by declines in the estimated cash flows from the borrowers as a resultunderlying property leases, fair value of thecollateral and creditworthiness of the borrowers or tenants of credit tenant loan properties. Ifproperties, where lease payments directly service the loan. Collecting amounts we collect from the borrowers that are less than the amountamounts recorded it would result in a charge to our earnings.

As a result of all of these factors, we may not earn an adequate return on our investments, may be required to write down the value of our investments and may incur losses on the disposition of our investments.

Changes in tax laws of jurisdictions in which we operate could adversely impact our results of operations.

The breach of confidential information also could give rise to legal liability and regulatory action under data protection and privacy laws, and regulations, bothas well as evolving regulation in this regard, including the U.S. and foreign jurisdictions.recently issued New York Department of Financial Services cyber regulation. Any such legal or regulatory action could have a material adverse effect on our operations.

Inability to detect and prevent significant employee or third party service provider misconduct or inadvertent errors and omissions could result in a materially adverse effect on our operations.

We may incur losses which arise from employees or third party service providers engaging in intentional misconduct, fraud, errors and omissions, failure to comply with internal guidelines, including with respect to underwriting authority, or failure to comply with regulatory requirements. Our controls may not be able to detect all possible circumstances of employee and third party service provider non-compliant activity and the internal structures in place to prevent this activity may not be effective in all cases. Any losses relating to such non-compliant activity could adversely affect our results of operations.

Loss of key vendor relationships, issues relating to the transitioning of vendor relationships or exposure relating to functions performed by a vendor could result in a materially adverse effect on our operations.

We face considerable competition within our industry for qualified, specialized talent and any significant inability to attract and retain talent may adversely affect the execution of our business strategies.

We are subject to capital adequacy requirements and, if we are unable to maintain or raise sufficient capital to meet these requirements, regulatory agencies may restrict or prohibit us from operating our business.

Insurance companies such as ours are subject to capital adequacy standards set by regulators to help identify companies that merit further regulatory attention. These standards apply specified risk factors to various asset, premium and reserve components of our legal entity statutory basis of accounting financial statements. Current rules, including those promulgated by insurance regulators and specialized markets, such as Lloyd's, require companies to maintain statutory capital and surplus at a specified minimum level determined using the applicable jurisdiction's regulatory capital adequacy formula. If we do not meet these minimum requirements, we may be restricted or prohibited from operating our business in the applicable jurisdictions and specialized markets. If we are required to record a material charge against earnings in connection with a change in estimated insurance reserves, the occurrence of a catastrophic event, or if we incur significant losses related to our investment portfolio, which

Globally, insurance regulators are working cooperatively to develop a common framework for the supervision of internationally active insurance groups. Finalization and adoption of this framework could increase our minimumprescribed capital requirement, the level at which regulatory capital requirementscrutiny intensifies, as well as significantly increase our cost of regulatory compliance.

Our insurance subsidiaries, upon whom we depend for dividends in order to fund our corporate obligations, are limited by insurance regulators in their ability to pay dividends.

We are a holding company and are dependent upon dividends, loans and other sources of cash from our subsidiaries in order to meet our obligations. Ordinary dividend payments, or dividends that do not require prior approval by the insurance subsidiaries' domiciliary insurance regulator, are generally limited to amounts determined by formulas that vary by jurisdiction. If we are restricted from paying or receiving intercompany dividends, by regulatory rule or otherwise, we may not be able to fund our corporate obligations and debt service requirements from available cash. As a result, we would need to look to other sources of capital which may be more expensive or may not be available at all.

Rating agencies may downgrade their ratings of us and thereby adversely affect our ability to write insurance at competitive rates or at all.

Ratings are an important factor in establishing the competitive position of insurance companies. Our insurance company subsidiaries, as well as our public debt, are rated by rating agencies, including, A.M. Best Company (A.M. Best), Moody's Investors Service, Inc. (Moody's) and Standard & Poor's (S&P). Ratings reflect the rating agency's opinions of an insurance company's or insurance holding company's financial strength, capital adequacy, enterprise risk management practices, operating performance, strategic position and ability to meet its obligations to policyholders and debt holders.

The rating agencies may take action to lower our ratings in the future as a result of any significant financial loss or possible changes in the methodology or criteria applied by the rating agencies. The severity of the impact on our business is dependent on the level of downgrade and, for certain products, which rating agency takes the rating action. Among the adverse effects in the event of such downgrades would be the inability to obtain a material volume of business from certain major insurance brokers, the inability to sell a material volume of our insurance products to certain markets and the required collateralization of certain future payment obligations or reserves.

In addition, it is possible that a significant lowering of the corporate debt ratings of Loews by certain of the rating agencies could result in an adverse impactaffect on our ratings, independent of any change in our circumstances.

We are subject to extensive existing state, local, federal and foreign governmental regulations that restrict our ability to do business and generate revenues; additional regulation or significant modification to existing regulations or failure to comply with regulatory requirements may have a materially adverse effect on our business, our operations and financial condition.

The insurance industry is subject to comprehensive and detailed regulation and supervision. Most insurance regulations are designed to protect the interests of our policyholders and third-party claimants, rather than our

investors. Each jurisdiction in which we do business has established supervisory agencies that regulate the manner in which we do business. Any changes in regulation could also impose significant burdens on us. In addition, the Lloyd's marketplace sets rules under which its members, including our Hardy syndicate, operate.

These rules and regulations relate to, among other things, the standards of solvency (including risk-based capital measures), government-supported backstops for certain catastrophic events (including terrorism), investment restrictions, accounting and reporting methodology, establishment of reserves and potential assessments of funds to settle covered claims against impaired, insolvent or failed private or quasi-governmental insurers.

Regulatory powers also extend to premium rate regulations which require that rates not be excessive, inadequate or unfairly discriminatory. State jurisdictions ensure compliance with such regulations through market conduct exams, which may result in losses to the extent non-compliance is ascertained, either as a result of failure to document transactions properly or failure to comply with internal guidelines, or otherwise. The jurisdictions in which we do business may also require us to provide coverage to persons whom we would not otherwise consider

ITEM 1B. UNRESOLVED STAFF COMMENTS

None.

ITEM 2. PROPERTIES

Our Chicago location houses our principal executive offices. We lease office space in various cities throughout the United States and in other countries. The following table sets forth certain information with respect to our principal office locations.

We lease all of the office space described above, including the building in Chicago, Illinois, which was sold by CCC during the first quarter of 2016.Illinois. We consider our properties to be in generally good condition, well maintained and suitable and adequate to carry on our business.

Not applicable.

Our common stock is listed on the New York Stock Exchange and the Chicago Stock Exchange under the symbol CNA.

As of February 10, 2017,9, 2018, we had 270,621,400271,217,644 shares of common stock outstanding and approximately 90%89% of our outstanding common stock was owned by Loews. We had 1,042978 stockholders of record as of February 10, 20179, 2018 according to the records maintained by our transfer agent.

The table below shows the high and low closing prices for our common stock based on the New York Stock Exchange Composite Transactions, as well as the dividends declared on our common stock.

The following graph compares the five-year total return of our common stock, the Standard & Poor's 500 (S&P 500) Index and the S&P 500 Property & Casualty Insurance Index. The graph assumes that the value of the investment in our common stock and each index was $100 at the base period, January 1, 2012,2013, and that dividends, if any, were reinvested.

ITEM 6. SELECTED FINANCIAL DATA

The following table presents selected financial data. On July 2, 2012, we acquired Hardy. The results of Hardy are included from the date of acquisition. The table should be read in conjunction with Item 7 Management's Discussion and Analysis of Financial Condition and Results of Operations and Item 8 Financial Statements and Supplementary Data of this Form 10-K. The comparative period Financial Condition data through 2013 includes CAC assets and liabilities.

ITEM 7. MANAGEMENT'S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND RESULTS OF OPERATIONS

Index to this MD&A

The following discussion should be read in conjunction with Item 1A Risk Factors, Item 6 Selected Financial Data and Item 8 Financial Statements and Supplementary Data of this Form 10-K.

CRITICAL ACCOUNTING ESTIMATES

The preparation of Consolidated Financial Statements in conformity with accounting principles generally accepted in the United States of America (GAAP) requires us to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the Consolidated Financial Statements and the amount of revenues and expenses reported during the period. Actual results may differ from those estimates.

Our Consolidated Financial Statements and accompanying notes have been prepared in accordance with GAAP applied on a consistent basis. We continually evaluate the accounting policies and estimates used to prepare the Consolidated Financial Statements. In general, our estimates are based on historical experience, evaluation of current trends, information from third-party professionals and various other assumptions that are believed to be reasonable under the known facts and circumstances.

Insurance reserves are established for both short and long-duration insurance contracts. Short-duration contracts are primarily related to property and casualty insurance policies where the reserving process is based on actuarial estimates of the amount of loss, including amounts for known and unknown claims. Long-duration contracts are primarily related to long term care policies and are estimated using actuarial estimates about morbidity and persistency as well as assumptions about expected investment returns and future premium rate increases. The reserve for unearned premiums on property and casualty contracts represents the portion of premiums written related to the unexpired terms of coverage. The reserving process is discussed in further detail in the Reserves-Estimates and Uncertainties section below.

Additionally, exposure exists with respect to the collectibility of amounts due from policyholders related to insurance contracts, including amounts due from insureds under high deductible policies and retrospectively rated policies. An allowance for uncollectible insurance receivables is recorded on the basis of periodic evaluations of balances due from insureds, currently as well as in the future, management's experience and current economic conditions.

If actual experience differs from the estimates made by management in determining the allowances for uncollectible reinsurance and insurance receivables, net receivables as reflected on our Consolidated Balance Sheets may not be collected. Therefore, our results of operations or equity could be materially adversely affected.

Our investment portfolio is subject to market declines below amortized cost that may be other-than-temporary and therefore result in the recognition of impairment losses in earnings. Factors considered in the determination of whether or not a decline is other-than-temporary include a current intention or need to sell the security or an indication that a credit loss exists. Significant judgment exists regarding the evaluation of the financial condition and expected near-term and long-term prospects of the issuer, the relevant industry conditions and trends and whether we expect to receive cash flows sufficient to recover the entire amortized cost basis of the security. Further information on our process for evaluating impairments is in Note A to the Consolidated Financial Statements included under Item 8.

Future policy benefitsbenefit reserves for our long term care policies are based on certain assumptions, including morbidity, persistency, inclusive of mortality, discount rates and future premium rate increases. The adequacy of the reserves is contingent upon actual experience and our future expectations related to these key assumptions. If actual or expected future experience differs from these assumptions, the reserves may not be adequate, requiring us to add to reserves.

A prolonged period during which interest rates remain at levels lower than those anticipated in our reserving discount rate assumption could result in shortfalls in investment income on assets supporting our obligations under long term care policies, which may also require an increase to our reserves. In addition, we may not receive regulatory approval for the premium rate increases we request.

These changes to our reserves could materially adversely impact our results of operations and equity. The reserving process is discussed in further detail in the Reserves - Estimates and Uncertainties section below.

We account for income taxes under the asset and liability method. Under this method, deferred income taxes are recognized for temporary differences between the financial statement and tax return basis of assets and liabilities. Any resulting future tax benefits are recognized to the extent that realization of such benefits is more likely than not, and a valuation allowance is established for any portion of a deferred tax asset that management believes will not be realized. The assessment of the need for a valuation allowance requires management to make estimates and assumptions about future earnings, reversal of existing temporary differences and available tax planning strategies. If actual experience differs from these estimates and assumptions, the recorded deferred tax asset may not be fully realized resulting in an increase to income tax expense in our results of operations. In addition, the ability to record deferred tax assets in the future could be limited, resulting in a higher effective tax rate in that future period.

RESERVES - ESTIMATES AND UNCERTAINTIES

Property and Casualty Claim and Claim Adjustment Expense Reserves

As discussed in the Risk Factors discussion within Item 1A, there is a risk that our recorded reserves are insufficient to cover our estimated ultimate unpaid liability for claims and claim adjustment expenses. Unforeseen emerging or potential claims and coverage issues are difficult to predict and could materially adversely affect the adequacy of our claim and claim adjustment expense reserves and could lead to future reserve additions.

In addition, our property and casualty insurance subsidiaries also have actual and potential exposures related to A&EP claims, which could result in material losses. To mitigate the risks posed by our exposure to A&EP claims and claim adjustment expenses, we completed a transaction with NICO under which substantially all of our legacy A&EP liabilities were ceded to NICO effective January 1, 2010. See Note E to the Consolidated Financial Statements included under Item 8 for further discussion about the transaction with NICO, its impact on our results of operations and the deferred retroactive reinsurance gain.

In developing claim and claim adjustment expense (“loss” or “losses”) reserve estimates, our actuaries perform detailed reserve analyses that are staggered throughout the year. The data is organized at a reserve group level. A reserve group can be a line of business covering a subset of insureds such as commercial automobile liability for small or middle market customers, it can encompass several lines of business provided to a specific set of customers such as dentists,aging services, or it can be a particular type of claim such as construction defect. Every reserve group is reviewed at least once during the year. The analyses generally review losses gross of ceded reinsurance and apply the ceded reinsurance terms to the gross estimates to establish estimates net of reinsurance. In addition to the detailed analyses, we review actual loss emergence for all products each quarter.

Most of our business can be characterized as long-tail. For long-tail business, it will generally be several years between the time the business is written and the time when all claims are settled. Our long-tail exposures include commercial automobile liability, workers' compensation, general liability, medical professional liability, other professional liability and management liability coverages, assumed reinsurance run-off and products liability. Short-tail exposures include property, commercial automobile physical damage, marine, surety and warranty. Specialty, Commercial and International contain both long-tail and short-tail exposures. Corporate & Other Non-Core contains long-tail exposures.

Various methods are used to project ultimate losses for both long-tail and short-tail exposures.

The paid development method estimates ultimate losses by reviewing paid loss patterns and applying them to accident or policy years with further expected changes in paid losses. Selection of the paid loss pattern may require

consideration of several factors, including the impact of inflation on claims costs, the rate at which claims professionals make claim payments and close claims, the impact of judicial decisions, the impact of underwriting changes, the impact of large claim payments and other factors. Claim cost inflation itself may require evaluation of changes in the cost of repairing or replacing property, changes in the cost of medical care, changes in the cost of wage replacement, judicial decisions, legislative changes and other factors. Because this method assumes that losses are paid at a consistent rate, changes in any of these factors can impactaffect the results. Since the method does not rely on case reserves, it is not directly influenced by changes in their adequacy.

For many reserve groups, paid loss data for recent periods may be too immature or erratic for accurate predictions. This situation often exists for long-tail exposures. In addition, changes in the factors described above may result in inconsistent payment patterns. Finally, estimating the paid loss pattern subsequent to the most mature point available in the data analyzed often involves considerable uncertainty for long-tail products such as workers' compensation.

The incurred development method is similar to the paid development method, but it uses case incurred losses instead of paid losses.  Since the method uses more data (case reserves in addition to paid losses) than the paid development method, the incurred development patterns may be less variable than paid patterns. However, selection of the incurred loss pattern typically requires analysis of all of the same factors described above. In addition, the inclusion of case reserves can lead to distortions if changes in case reserving practices have taken place, and the use of case incurred losses may not eliminate the issues associated with estimating the incurred loss pattern subsequent to the most mature point available.

The loss ratio method multiplies earned premiums by an expected loss ratio to produce ultimate loss estimates for each accident or policy year. This method may be useful for immature accident or policy periods or if loss development patterns are inconsistent, losses emerge very slowly or there is relatively little loss history from which to estimate future losses. The selection of the expected loss ratio typically requires analysis of loss ratios from earlier accident or policy years or pricing studies and analysis of inflationary trends, frequency trends, rate changes, underwriting changes and other applicable factors.

The Bornhuetter-Ferguson method using paid loss is a combination of the paid development method and the loss ratio method. This method normally determines expected loss ratios similar to the approach used to estimate the expected loss ratio for the loss ratio method and typically requires analysis of the same factors described above. This method assumes that future losses will develop at the expected loss ratio level. The percent of paid loss to ultimate loss implied from the paid development method is used to determine what percentage of ultimate loss is yet to be paid. The use of the pattern from the paid development method typically requires consideration of the same factors listed in the description of the paid development method. The estimate of losses yet to be paid is added to current paid losses to estimate the ultimate loss for each year. For long-tail lines, this method will react very slowly if actual ultimate loss ratios are different from expectations due to changes not accounted for by the expected loss ratio calculation.

The Bornhuetter-Ferguson method using incurred loss is similar to the Bornhuetter-Ferguson method using paid loss except that it uses case incurred losses. The use of case incurred losses instead of paid losses can result in development patterns that are less variable than paid patterns. However, the inclusion of case reserves can lead to distortions if changes in case reserving have taken place, and the method typically requires analysis of the same factors that need to be reviewed for the loss ratio and incurred development methods.

The frequency times severity method multiplies a projected number of ultimate claims by an estimated ultimate average loss for each accident or policy year to produce ultimate loss estimates. Since projections of the ultimate number of claims are often less variable than projections of ultimate loss, this method can provide more reliable results for reserve groups where loss development patterns are inconsistent or too variable to be relied on exclusively. In addition, this method can more directly account for changes in coverage that impactaffect the number and size of claims. However, this method can be difficult to apply to situations where very large claims or a substantial number of unusual claims result in volatile average claim sizes. Projecting the ultimate number of claims may require analysis of several factors, including the rate at which policyholders report claims to us, the impact of judicial decisions, the impact of underwriting changes and other factors. Estimating the ultimate average loss may require analysis of the impact of large losses and claim cost trends based on changes in the cost of repairing or replacing

property, changes in the cost of medical care, changes in the cost of wage replacement, judicial decisions, legislative changes and other factors.

Stochastic modeling produces a range of possible outcomes based on varying assumptions related to the particular reserve group being modeled. For some reserve groups, we use models which rely on historical development patterns at an aggregate level, while other reserve groups are modeled using individual claim variability assumptions supplied by the claims department. In either case, multiple simulations using varying assumptions are run and the results are analyzed to produce a range of potential outcomes. The results will typically include a mean and percentiles of the possible reserve distribution which aid in the selection of a point estimate.

For many exposures, especially those that can be considered long-tail, a particular accident or policy year may not have a sufficient volume of paid losses to produce a statistically reliable estimate of ultimate losses. In such a case, our actuaries typically assign more weight to the incurred development method than to the paid development method. As claims continue to settle and the volume of paid loss increases, the actuaries may assign additional weight to the paid development method.  For most of our products, even the incurred losses for accident or policy years that are early in the claim settlement process will not be of sufficient volume to produce a reliable estimate of ultimate losses. In these cases, we may not assign much if any weight to the paid and incurred development methods. We willmay use the loss ratio, Bornhuetter-Ferguson andand/or frequency times severity methods.  For short-tail exposures, the paid and incurred development methods can often be relied on sooner, primarily because our history includes a sufficient number of years to cover the entire period over which paid and incurred losses are expected to change. However, we may also use the loss ratio, Bornhuetter-Ferguson andand/or frequency times severity methods for short-tail exposures.

For other more complex reserve groups where the above methods may not produce reliable indications, we use additional methods tailored to the characteristics of the specific situation.

The reserve analyses performed by our actuaries result in point estimates. Each quarter, the results of the detailed reserve reviews are summarized and discussed with senior management to determine the best estimate of reserves. Senior management considers many factors in making this decision. Our recorded reserves reflect our best estimate as of a particular point in time based upon known facts and circumstances, consideration of the factors cited above and our judgment. The carried reserve may differdiffers from the actuarial point estimate. See Note E to the Consolidated Financial Statements included under Item 8 forestimate as discussed further discussion of the factors considered in determining management’s best estimate.below.

Currently, our recorded reserves are modestly higher than the actuarial point estimate. For Commercial, Specialty and International, the difference between our reserves and the actuarial point estimate is primarily driven by uncertainty with respect to immature accident years, claim cost inflation, changes in claims handling, changes to the tort environment which may adversely impactaffect claim costs and the effects from the economy. For Corporate & Other, Non-Core, the difference between our reserves and the actuarial point estimate is primarily driven by the potential tail volatility of run-off exposures.

The key assumptions fundamental to the reserving process are often different for various reserve groups and accident or policy years. Some of these assumptions are explicit assumptions that are required of a particular method, but most of the assumptions are implicit and cannot be precisely quantified. An example of an explicit assumption is the pattern employed in the paid development method. However, the assumed pattern is itself based on several implicit assumptions such as the impact of inflation on medical costs and the rate at which claim professionals close claims. As a result, the effect on reserve estimates of a particular change in assumptions typically cannot be specifically quantified, and changes in these assumptions cannot be tracked over time.

Our recorded reserves are management's best estimate. In order to provide an indication of the variability associated with our net reserves, the following discussion provides a sensitivity analysis that shows the approximate estimated impact of variations in significant factors affecting our reserve estimates for particular types of business. These significant factors are the ones that we believe could most likely materially affect the reserves. This discussion covers the major types of business for which we believe a material deviation to our reserves is reasonably possible. There can be no assurance that actual experience will be consistent with the current assumptions or with the variation

The three areas for which we believe a significant deviation to our net reserves is reasonably possible are (i) professional liability, management liability and surety products; (ii) workers' compensation; and (iii) general liability.

Professional liability, management liability and surety products include professional liability coverages provided to various professional firms, including architects, real estate agents, small and mid-sized accounting firms, law firms and other professional firms. They also include directors and officers (D&O), employment practices, fiduciary, fidelity and surety coverages, as well as insurance products serving the healthcare delivery system. The most significant factor affecting reserve estimates for these liability coverages is claim severity. Claim severity is driven by the cost of medical care, the cost of wage replacement, legal fees, judicial decisions, legislative changes and other factors. Underwriting and claim handling decisions such as the classes of business written and individual claim settlement decisions can also impactaffect claim severity. If the estimated claim severity increases by 9%, we estimate that net reserves would increase by approximately $450 million. If the estimated claim severity decreases by 3%, we estimate that net reserves would decrease by approximately $150 million. Our net reserves for these products were approximately $5.2$5.0 billion as of December 31, 2016.2017.

For workers' compensation, since many years will pass from the time the business is written until all claim payments have been made, the most significant factor affecting workers' compensation reserve estimates is claim cost inflation on claim payments. Workers' compensation claim cost inflation is driven by the cost of medical care, the cost of wage replacement, expected claimant lifetimes, judicial decisions, legislative changes and other factors. If estimated workers' compensation claim cost inflation increases by 100 basis points for the entire period over which claim payments will be made, we estimate that our net reserves would increase by approximately $400$350 million. If estimated workers' compensation claim cost inflation decreases by 100 basis points for the entire period over which claim payments will be made, we estimate that our net reserves would decrease by approximately $350 million. Our net reserves for workers' compensation were approximately $4.3$4.0 billion as of December 31, 2016.2017.

For general liability, the most significant factor affecting reserve estimates is claim severity. Claim severity is driven by changes in the cost of repairing or replacing property, the cost of medical care, the cost of wage replacement, judicial decisions, legislation and other factors. If the estimated claim severity for general liability increases by 6%, we estimate that our net reserves would increase by approximately $200 million. If the estimated claim severity for general liability decreases by 3%, we estimate that our net reserves would decrease by approximately $100 million. Our net reserves for general liability were approximately $3.4$3.3 billion as of December 31, 2016.2017.

Given the factors described above, it is not possible to quantify precisely the ultimate exposure represented by claims and related litigation. As a result, we regularly review the adequacy of our reserves and reassess our reserve estimates as historical loss experience develops, additional claims are reported and settled and additional information becomes available in subsequent periods. In reviewing our reserve estimates, we make adjustments in the period that the need for such adjustments is determined. These reviews have resulted in our identification of information and trends that have caused us to change our reserves in prior periods and could lead to our identification of a need for additional material increases or decreases in claim and claim adjustment expense reserves, which could materially affect our results of operations, equity, business and insurer financial strength and corporate debt ratings positively or negatively. See discussion within Note E to the Consolidated Financial Statements included under Item 8 for additional information about reserve development and the Ratings section of this MD&A for further information regarding our financial strength and corporate debt ratings.

Life & Group Non-Core Policyholder Reserves

Our Life and& Group Non-Core segment includes our run-off long term care business as well as structured settlement obligations not funded by annuities related to certain property and casualty claimants not funded by annuities.claimants. Long term care policies provide benefits for nursing homes, assisted living facilities and home health care subject to various daily and lifetime caps. PolicyholdersGenerally, policyholders must continue to make periodic premium payments to keep the policy in force. Generallyforce and we have the ability to increase policy premiums, subject to state regulatory approval.

We maintain both claim and claim adjustment expense reserves as well as future policy benefitsbenefit reserves for policyholder benefits for our Life & Group Non-Core segment. Claim and claim adjustment expense reserves consist of estimated reserves for long term care policyholders that are currently receiving benefits, including claims that have

been incurred but are not yet reported. In developing the claim and claim adjustment expense reserve estimates for our long term care policies, our actuaries perform a detailed claim experience study on an annual basis. The study reviews the sufficiency of existing reserves for policyholders currently on claim and includes an evaluation of expected benefit utilization and claim duration. Our recorded claim and claim adjustment expense reserves reflect management's best estimate after incorporating the results of the most recent study. In addition, claim and claim adjustment expense reserves are also maintained for the structured settlement obligations.

Future policy benefitsbenefit reserves represent the active life reserves related to our long term care policies and are the present value of expected future benefit payments and expenses less expected future premium. The determination of these reserves is fundamental to our financial results and requires management to make estimates and assumptions about expected investment and policyholder experience over the life of the contract. The assumptions used to determine the active life reserves were unlocked as of December 31, 2015 in connection with the recognition of a premium deficiency. Since many of these contracts may be in force for several decades, these assumptions are subject to significant estimation risk.

Annually, management assesses the adequacy of its GAAP long term care future policy benefitsbenefit reserves as well as the claim and claim adjustment expense reserves for structured settlement obligations by performing a gross premium valuation (GPV) to determine if there is a premium deficiency. Management also uses the GPV process to evaluate the adequacy of the claim and claim adjustment expense reserves for structured settlement obligations. Under the GPV, management estimates required reserves using best estimate assumptions as of the date of the assessment without provisions for adverse deviation. The GPV required reserves are then compared to the recorded reserves. If the GPV required reserves are greater than the existing net GAAPrecorded reserves, (i.e. reserves net of any deferred acquisition costs asset), the existing net GAAP reservesassumptions are unlocked and future policy benefit reserves are increased to the greater amount. Any such increase is reflected in our results of operations in the period in which the need for such adjustment is determined, and could materially adversely affect our results of operations, equity and business and insurer financial strength and corporate debt ratings. Periodically, management engages independent third parties to assess the appropriateness of its best estimate assumptions and the associated GPV required reserves. The most recent assessment by an independent third party was performed in 2017.

The December 31, 20162017 GPV indicated carriedour recorded reserves included a margin of approximately $255$246 million. A summary of the changes in the GPV resultsestimated reserve margin is presented in the table below:

The increasedecrease in the margin in 20162017 was driven by the reduction in the Federal corporate income tax rate enacted on December 22, 2017 which reduced the tax equivalent yield on the tax exempt municipal bonds in the investment portfolio supporting the long term care liabilities. A continuation of the low interest rate environment also drove a reduction in the discount rate assumptions. These unfavorable drivers were mostly offset by favorable changes

to the underlying morbidity assumptions, both frequency and severity, higher than expected rate increases from near-term futureon active rate filings on segments of our individual long term care block of business as well as higher than expected premium rate increase achievement on rate filings relatedaction programs and favorable changes to our group long term care block.  This improvement from rate actions was partially offset by minor changes in morbiditythe underlying expense assumptions.

The effects of persistency and discount rates were relatively small and largely offset one another.  Additionally, in 2016 our annual experience study of long term care claim reservesexperience study resulted in a release of $30$42 million due tofrom claim reserves driven by favorable frequency and severity relative to expectations.

As referencedreflected in Item 1A Risk Factors, modification of the Long Term Care Active Life Reserve - Change in estimated reserve margin table on the preceding page, the reduction in the Federal corporate income tax rate could adversely affectaffected the value of the tax benefit received on tax exempt municipal investments and thus the rate at which we discount our long term care active life reserves. For illustrative reference, absent a change in investment strategy, aAny future reduction in theincome tax rates could further adversely affect our GPV discount rates.

The Company purchases corporate tax ratecatastrophe excess-of-loss treaty reinsurance covering its U.S. states and territories and Canadian property exposures underwritten in our North American and non-Lloyds European companies. The treaty has a term of January 1, 2018 to 20% would require an increase to our existing net GAAP reservesDecember 31, 2018. The 2018 treaty provides coverage for the LTC business and an estimated reductionaccumulation of losses from catastrophe occurrences above the Company’s per occurrence retention of $250 million up to pretax income of approximately $700 million.

The Company also purchases corporate Workers Compensation catastrophe excess-of-loss treaty reinsurance for the period January 1, 2018 to December 31, 2018 providing $275 million of coverage for the accumulation of covered losses related to natural catastrophes above the Company retention of $25 million. The treaty also provides $475 million of coverage for the accumulation of covered losses related to terrorism events above the Company retention of $25 million. Of this $475 million in Terrorism coverage, $200 million is provided for nuclear, biological chemical and radiation events. One full reinstatement is available for the first $275 million above the retention, regardless of the covered peril. The Company also purchases a targeted facultative facility to address exposure accumulations in specific policies affected and, therefore, may differ from the estimates summarized above.peak Terrorism zones.

CONSOLIDATED OPERATIONS

Results of Operations

Core income increased $95 million in 2017 as compared to 2016. Core income for our Property & Casualty Operations declined $23 million primarily driven by higher net catastrophe losses partially offset by improved non-catastrophe current accident year underwriting results. Net operatingcatastrophe losses were $259 million after tax in 2017 as compared to $111 million after tax in 2016. Core loss for our operations outside of Property & Casualty Operations improved $118 million driven by lower adverse prior year A&EP reserve development.

The following discusses the results of operations for our business segments.

Our core property and casualty commercial insurance operations are managed and reported in three business segments: Specialty, Commercial and International.International, which we refer to collectively as Property & Casualty Operations. Specialty provides a broad array of professional, financial and specialty property and casualty products and services through a network of independent agents, brokers and managing general underwriters. Commercial includes property and casualty coverages sold to small businesses and middle market entities and organizations primarily through an independent agency distribution system. Commercial also includes commercial insurance and risk management products sold to large corporations primarily through insurance brokers. International provides management and professional liability coverages as well as a broad range of other property and casualty insurance products and services abroad through a network of brokers, independent agencies and managing general underwriters, as well as the Lloyd’s marketplace.

Effective January 1, 2018, management is changing the segment presentation of our life sciences business and technology and media related errors and omissions (E&O) business within the Specialty and Commercial business segments.  Our non-corelife sciences business provides product liability and other coverages such as property and workers compensation associated with the life sciences industry. Approximately $100 million of net written premium related to the life sciences business will move from the Specialty business segment to the Commercial business segment.  Our technology and media related E&O business provides network security and privacy, media and E&O coverage primarily for technology risks.  Approximately $70 million of net written premium related to this business will move from the Commercial business segment to the Specialty business segment. We believe the new management responsibility for these businesses better aligns with line of business underwriting expertise and the manner in which the products are sold. The new classifications will be presented in the Company’s financial statements beginning with the period ending March 31, 2018, and prior periods presented will conform to the new presentation.

Our operations outside of Property & Casualty Operations are managed and reported in two segments: Life & Group Non-Core and Corporate & Other Non-Core.Other. Life & Group Non-Core primarily includes the results of our long term care business that is in run-off. Corporate & Other Non-Core primarily includes certain corporate expenses, including interest on corporate debt, and the results of certain property and casualty businessbusinesses in run-off, including CNA Re and A&EP. Intersegment eliminations are also included in this segment.

Our property and casualtyProperty & Casualty Operations field structure consists of 49 underwriting locations across the United States. In addition, there are five centralized processing operations which handle policy processing, billing and collection activities and also act as call centers to optimize service. The claims structureOur claim presence consists of a nationalsix primary locations where we handle multiple claim center designed to efficiently handle the high volume of low severity claims, including property damage, liabilitytypes and workers' compensation medical only claims, and 16 principalkey business functions. Additionally, claim maintains regional offices handling the more complex claims.which are aligned with our underwriting field structure. We also have a presence in Canada, Europe China and Singapore consisting of 17 branch operations and access to business placed at Lloyd's of London through Hardy Syndicate 382.

What we previously referred to as net operating income (loss) in our public disclosures, we now refer to as core income (loss). The fourth quarter 2017 net deferred tax asset remeasurement was excluded from core income (loss) for the year ended December 31, 2017. Otherwise, there were no changes to the calculation of this measure. We utilize the net operatingcore income (loss) financial measure to monitor our operations. Net operatingCore income (loss) is calculated by excluding from net income (loss) the after-tax effects of 1)i) net realized investment gains or losses, 2)ii) income or loss from discontinued operations, and 3)iii) any cumulative effects of changes in accounting guidance.guidance and iv) deferred tax asset and liability remeasurement as a result of an enacted U.S. Federal tax rate change. The calculation of net operatingcore income (loss) excludes net realized investment gains or losses because net realized investment gains or losses are largely discretionary, except for some losses related to other-than-temporary impairment (OTTI) losses, and are generally driven by economic factors that are not necessarily consistent with key drivers of underwriting performance, and are therefore not considered an indication of trends in insurance operations. Management monitors net operatingcore income (loss) for each business segment to assess segment performance. Presentation of consolidated net operatingcore income (loss) is deemed to be a non-GAAP financial measure. See further discussion regarding how we manage our business and reconciliations of non-GAAP measures to the most comparable GAAP measures and other information in Note O to the Consolidated Financial Statements included under Item 8.

In evaluating the results of our Specialty, Commercial and International segments, we utilize the loss ratio, the expense ratio, the dividend ratio and the combined ratio. These ratios are calculated using GAAP financial results.

The loss ratio is the percentage of net incurred claim and claim adjustment expenses to net earned premiums. The expense ratio is the percentage of insurance underwriting and acquisition expenses, including the amortization of deferred acquisition costs, to net earned premiums. The dividend ratio is the ratio of policyholders' dividends incurred to net earned premiums. The combined ratio is the sum of the loss, expense and dividend ratios. In addition we also utilize renewal premium change, rate, retention and new business in evaluating operating trends. Renewal premium change represents the estimated change in average premium on policies that renew, including rate and exposure changes. Rate represents the average change in price on policies that renew excluding exposure change. Retention represents the percentage of premium dollars renewed in comparison to the expiring premium dollars from policies available to renew. Renewal premium change, rate and retention presented for the prior year are updated to reflect subsequent activity on policies written in the period. New business represents premiums from policies written with new customers and additional policies written with existing customers.

Changes in estimates of claim and allocated claim adjustment expense reserves and premium accruals, net of reinsurance, for prior years are defined as net prior year development within this MD&A. These changes can be favorable or unfavorable. Net prior year development does not include the impacteffect of related acquisition expenses. Further information on our reserves is provided in Note E to the Consolidated Financial Statements included under Item 8.

Specialty provides management and professional liability and other coverages through property and casualty products and services using a network of brokers, independent agencies and managing general underwriters. Specialty includes the following business groups:

Management & Professional Liability provides management and professional liability insurance and risk management services and other specialized property and casualty coverages. This group provides professional liability coverages to various professional firms, including architects, real estate agents, accounting firms, law firms and other professional firms. Management & Professional Liability also provides D&O, employment practices, fiduciary and fidelity coverages. Specific areas of focus include small and mid-size firms, public as well as privately held firms and not-for-profit organizations, where tailored products for these client segments are offered. Products within Management & Professional Liability are distributed through brokers, independent agents and managing general underwriters. Management & Professional Liability through CNA HealthCare, also offers insurance products to serve the healthcare industry. Products include professional and general liability as well as associated standard property and casualty coverages, and are distributed on a national basis through brokers, independent agents and managing general underwriters. Key customer groups include aging services, allied medical facilities, life sciences, dentists, physicians, hospitals and nurses and other medical practitioners.

The following table details the results of operations for Specialty.

Net written premiums for Specialty in 2016 were consistent with 2015 as growth in warranty was offset by a decrease in management and professional liability and healthcare due to underwriting actions undertaken in certain business lines. The trend in net earned premiums was consistent with net written premiums.

Net operatingCore income increased $90 million in 2016 as compared with 2015, primarily due to higher favorable net prior year reserve development and net investment income partially offset by higher underwriting expenses and current accident year net loss and loss adjustment expenses.

The combined ratio decreased 3.7 points in 2016 as compared with 2015. The loss ratio decreased 4.6 points due to higher favorable net prior year reserve development partially offset by a higher current accident year loss ratio. CatastropheNet catastrophe losses were $18 million, or 0.6 points of the loss ratio, for 2016 as compared to $13 million, or 0.4 points of the loss ratio, for 2015. The expense ratio increased 0.9 points in 2016 as compared with 2015, due to higher employee costs and higher IT spending primarily related to new underwriting platforms.