Board Leadership and Governance

The directors and officers of NuStar GP, LLC, the general partner of our general partner, Riverwalk Logistics, L.P., perform all of our management functions, and we do not have directors or officers. However, for simplicity's sake, in this proxy statement, we refer to the directors of NuStar GP, LLC as our directors or our Board, and we refer to the officers of NuStar GP, LLC as our officers.

Our business is managed under the direction of our Board. Our Board is led by its Chairman, William E. Greehey. As illustrated in the table under "Board Refreshment and Composition" below, 80% of our directors meet the independence requirements of the NYSE listing standards, with the Chairman of our Board and our Chief Executive Officer arebeing the only two members of our Board who are not independent directors. Although the Board believes that separating the roles of Chairman and Chief Executive Officer is appropriate in the current circumstances in light of Mr. Greehey's extensive knowledge and experience regarding our operations and our industry, our Corporate Governance Guidelines do not establish this approach as a policy. The Board also has appointed Dan J. Hill as its independent, presiding director to serve as a point of contact for unitholders wishing to communicate with the Board, lead executive sessions of the non-management directors and ensure independent oversight.

TheOur Board conducts its business through meetings of the Board and its committees. The Board has standing Audit, Compensation and Nominating/Governance & Conflicts Committees.Committees, each of which is composed entirely of directors who meet the independence requirements of the NYSE listing standards. Each committee has a written charter, which is available under the Corporate Governance tab in the Investors section of our website at www.nustarenergy.com.

On August 31, 2021, our Board appointed Ed A. Grier and Martin Salinas, Jr. as new members of our Board. Their skills and experiences further enhance our Board's expertise and diversity. On October 27, 2021, James F. Clingman, Jr. retired from our Board, with the Board expressing its gratitude for his years of service. The table below lists the current members and chair of our Board and each standing committee of our Board, the director selected to serve as the independent, presiding director of the Board, the independence and audit committee financial expertise determinations made by our Board with respect to each director, and the number of Board and committee meetings held during 2020. Each member of our Board attended 100% of2021. For further information regarding the meetings of the Boardqualifications, skills and his or her committees during 2020. Allattributes of our Board members, attended our 2020 Annual Meeting and are invited to attend our 2021 Annual Meeting.see "Proposal No.1—Election of Directors" below.

Director Independence

Our Board includes one member of management, Bradley C. Barron, our President and Chief Executive Officer, and eightnine non-management directors. As a limited partnership, NuStar Energy is not required to have a majority of independent directors. However, as illustrated in the table above, the Board has determined that seveneight of its eightnine current non-management directors meet the independence requirements of the NYSE listing standards as set forth in the NYSE Listed Company Manual.

The Audit, Compensation and Nominating/Governance & Conflicts Committees of the Board are each composed entirely of directors who meet the independence requirements of the NYSE listing standards. Each member of the Audit Committee also meets the additional independence standards for Audit Committee members set forth in the regulations of the Securities and Exchange Commission (SEC). For further information about the committees, see "Committees of the Board" below.

No director qualifies as independent under the NYSE's listing standards unless the Board affirmatively determines that the director has no material relationship with NuStar Energy. As provided for under the NYSE's listing standards, the Board has adopted categorical standards or guidelines to assist the Board in making its independence determinations with respect to each director. A relationship falls within the guidelines adopted by the Board if it:

Our Corporate Governance Guidelines contain the director qualification standards, including the guidelines listed above, and are available under the Corporate Governance tab in the Investors section of our website at www.nustarenergy.com or are available in print upon request to our Corporate Secretary at corporatesecretary@nustarenergy.com or the address indicated on the cover page of this proxy statement.

Committees of the Board

The Audit Committee reviews and reports to the Board on various auditing and accounting matters, including the quality, objectivity and performance of our registered public accounting firm (our independent auditors) and our internal audit function, the adequacy of our internal controls over financial reporting and the reliability of financial information reported to the public. The Audit Committee has sole authority as to the retention, evaluation, compensation and oversight of the work of our independent auditors, who report directly to the Audit Committee. The Audit Committee reviews our internal audit plan and all significant internal audit reports. The Audit Committee also monitors financial risk exposures, risk assessment and risk management policies, as well as our compliance with legal and regulatory requirements, including those related to the health, safety and environmental performance of our company.requirements.

As a limited partnership, we are not required by NYSE rules to have a compensation committee. However, our Board has established a Compensation Committee to review and report to the Board on matters related to compensation strategies, policies and programs, including certain personnel policies and policy controls, management development, management succession and benefit programs. As described in "Compensation Discussion and Analysis" below, the Compensation Committee approves the compensation for our executive officers and approves and administers NuStar Energy’s equity compensation plans, incentive bonus plan and all performance measures established for awards under those plans. The Compensation Committee also conducts periodic reviews of director compensation and makes recommendations to the Board regarding director compensation.

As a limited partnership, we are not required by NYSE rules to have a nominating committee. However, our Board created a Nominating/Governance & Conflicts Committee to identify candidates for membership on the Board, recommend director nominees and oversee our Corporate Governance Guidelines and Board assessment process. Pursuant to our partnership

There are no compensation committeeCompensation Committee interlocks. Mr. Hill (Chairman), Mr. ClingmanBates and Mr. Rosier serve as the members of our Compensation Committee. Prior to his retirement from our Board on October 27, 2021, Mr. Clingman served as a member of our Compensation Committee. None of our Compensation Committee members have served as an officer or employee of ours. Furthermore, except for compensation arrangements disclosed in this proxy statement, we have not participated in any contracts, loans, fees or awards, and do not have any financial interests, direct or indirect, with any Compensation Committee member. In addition, none of our management or Board members are aware of any means, directly or indirectly, by which a Compensation Committee member could receive a material benefit from NuStar Energy.

Although management has the day-to-day responsibility forof assessing and managing our risk exposure, the Board and its committees oversee those efforts. The Board interfaces regularly with management and receives periodic reports that include updates on operational, financial, health, safety and environmental, legal, cybersecurity and other risk management matters. For example, the Board continues to receive regular reports regarding the COVID-19 pandemic and its impact on NuStar Energy and its employees.topics such as:

The Board as a whole typically discusses and addresses our key strategic risks at its meetings over the course of each year, both as they relate to particular projects or other topics being considered by the Board and in their own right as a separate agenda topic. At least once annually, the Board has a session devoted specifically to strategic planning, including identifying and addressing our strategic risks and potential opportunities, and evaluating matters such as ESG, sustainability and energy transition. The Board also receives detailed reports from management at least annually regarding specific topics, such as cybersecurity and our HSE performance, with monthly updates provided by our President and Chief Executive Officer regarding a variety of matters, including operational, health, safety and environmental,HSE, financial, legal, governance and cybersecurity matters, as applicable. The Board also continues to receive regular reports regarding the COVID-19 pandemic and its impact on NuStar Energy and its employees.

Although our Board retains direct oversight with respect to certain key topics that are broadly applicable across NuStar Energy's business, such as HSE performance; operational performance; strategic planning; ESG performance, sustainability and energy transition; and cybersecurity, the Board has delegated certain oversight responsibilities to its committees. Each committee of the Board also reports to the Board on a regular basis, including as appropriate with respect to each committee's risk oversight activities. For example,activities, as applicable, the Board and the Audit Committee discuss the guidelines and policies that govern the process by which risk assessment and management is undertaken and evaluate reports from various functions with the management team on risk assessment and management. The Audit Committee assists the Board in oversight of the integrity of NuStar Energy's financial statements and compliance with legal and regulatory requirements, including those related to the health, safety and environmental performance of our company, and the Audit Committee or the full Board receives a detailed report annually regarding NuStar Energy's health, safety and environmental performance. The Audit Committee also reviews and assesses the performance of NuStar Energy's internal audit function and its independent auditors. The Compensation Committee oversees risks associated with our compensation programs, and focuses on aligning our compensation policies with the long-term interests of NuStar Energy, as further described under "Evaluation of Compensation Risk"illustrated below. As described under "Compensation Discussion and Analysis" below, the Compensation Committee also evaluates NuStar Energy's financial, operational and health, safety and environmental performance as it assesses performance with respect to bonus awards and performance awards. The Compensation Committee also oversees executive succession planning. The Nominating/Governance & Conflicts Committee oversees risks related to corporate governance, such as director independence, the effectiveness of our Board and committees, director nominations and potential conflicts of interest.

We believe that our Board's role in risk oversight is consistent with our leadership structure, with our Chief Executive Officer and other members of management having responsibility for assessing and managing our risk exposure and the Board and its committees providing oversight in connection with those efforts.efforts, as illustrated below.

We have adopted a Code of Ethics for Senior Financial Officers that applies to our principal executive officer, principal financial officer and controller. This code charges the senior financial officers with responsibilities regarding honest and ethical conduct, the preparation and quality of the disclosures in documents and reports we file with or submit to the SEC, compliance with applicable laws, rules and regulations, adherence to the code and reporting of violations of the code.

We also have adopted a Code of Business Conduct and Ethics that applies to our directors and all of our employees, including our officers. Our Code of Business Conduct and Ethics emphasizes NuStar Energy's guiding principles, compliance with applicable laws, rules and regulations and the ethical conduct expected by NuStar Energy, is available in multiple languages and references NuStar Energy's anonymous reporting hotline service administered by a third party, as well as internal resources that are available to discuss any concerns and answer questions regarding the Code of Business Conduct and Ethics and NuStar Energy's policies. Our employeesCode of Business Conduct and Ethics covers topics such as business and financial records, nonpublic information, insider trading, privacy, cybersecurity, conflicts of interest, health and safety, discrimination, harassment, retaliation, acting with integrity and raising concerns. Employees also receive training regarding topics contained in our Code of Business Conduct and Ethics annually and are asked to attest to their compliance with our Code of Business Conduct and Ethics and various other NuStar Energy policies annually.

We post the following documents on our website at www.nustarenergy.com under the Corporate Governance tab in the Investors section:

We strive to maintain an appropriate balance of skills, experiences, diversity and tenure among our Board members. The Nominating/Governance & Conflicts Committee is responsible for assessing the skills and characteristics that candidates for election to the Board should possess, as well as the composition of the Board as a whole. The assessments include qualifications under applicable independence standards and other standards applicable to the Board and its committees, as well as consideration of skills and experience in the context of the needs of the Board. Each candidate must meet certain minimum qualifications, including:

The Nominating/Governance & Conflicts Committee may also consider the ability of a prospective candidate to work with the then-existing interpersonal dynamics of the Board and the candidate's ability to contribute to the collaborative culture among Board members. In accordance with our Corporate Governance Guidelines, individuals are considered for membership on the Board based on their character, judgment, integrity, diversity, age, skills (including financial literacy), independence and

Unitholders and other interested parties may communicate with the Board, the non-management directors or the independent, presiding director by sending a written communication addressed to "Board of Directors," "Non-Management Directors" or "Presiding Director" in care of our Corporate Secretary at corporatesecretary@nustarenergy.com or the address indicated on the cover page of this proxy statement. In general, any unitholder communication will be distributed in accordance with the unitholder's instructions; however, we reserve the right not to distribute any items that are unrelated to the duties and responsibilities of the Board or materials that are abusive, threatening or otherwise inappropriate. Additional requirements for certain types of communications are stated below under the caption "Additional Information—Advance Notice Required for Unitholder Proposals and Nominations.Nominations for the 2023 Annual Meeting."

Our Board is divided into three groups for purposes of election. Three Group IIII directors will be elected at our 20212022 Annual Meeting to serve a three-year term that will expire at our 20242025 Annual Meeting.

If any nominee is unavailable as a candidate at the time of our 20212022 Annual Meeting, either the number of directors constituting the full Board will be reduced to eliminate any vacancy or the persons named as proxies will use their best judgment in voting for any available nominee. The Board has no reason to believe that the current nominees will be unable to serve.

Mr. Barron,Bates, Mr. BurnettGrier and Mr. RosierHill are the nominees for election as Group IIII directors at our 20212022 Annual Meeting. There is no family relationship among any of our executive officers or directors, and there is no arrangement or understanding between any director or other person pursuant to which the director was or is to be selected as a director or nominee.

To determine 20202021 Adjusted EBITDA, we first calculated earnings before interest, taxes and depreciation and amortization (EBITDA) by adjusting our net income for interest expense, income tax expense and depreciation and amortization expense.

Adjusted DCFdistributable cash flow (DCF) for 20202021 was determined for this purpose by adjusting our net income for non-cash items, including depreciation and amortization expense, unrealized gains and losses arising from certain derivative contracts, impairment charges and losses related to dispositions. We then made additional adjustments, primarily consisting of (1) subtracting the amount of reliability capital expenditures, (2) adding certain compensation expenses, (3) adding or subtracting, as applicable, certain cash receipts and disbursements not included in net income, (4) subtracting the distributions and other costs related to our preferred units and (5) adjusting for certain non-operational financing expenses,the effect of disposed operations, to arrive at Adjusted DCF.

Adjusted operating and general and administrative expense for 20202021 was calculated for this purpose by making adjustments to operating and general and administrative expense related to (1) certain compensation expenses, (2) certain other non-cash items, including non-cash impairment charges, (3) certain expenses for which we receive full reimbursement, and (4) insurance payments that offset certain operating expenses.expenses and (5) the effect of disposed operations.

We provide NuStar Energy common unit-based, long-term incentive compensation to employees, including our NEOs, and to non-employee directors through the 2019 LTIP, which was approved by our unitholders at our annual meeting in April 2019. The 2019 LTIP provides for NuStar Energy common unit awards and a variety of NuStar Energy common unit-based awards, including unit options, phantom or restricted units and performance awards. Long-term incentive awards vest over a period determined by the Compensation Committee, with performance awards vesting upon the achievement of performance goals.

Under the design of our long-term incentive awards, a target long-term incentive award opportunity expressed as a percentage of base salary is established for each participant, including each NEO. This percentage reflects the fair value of the awards to be granted.

Following EPPA's 2018Meridian's analysis of our NEO's Total Direct Compensation,executive compensation program and pay levels during 2021, the Compensation Committee increased the long-term incentive targets for Mr. Barron from 250%325% to 325%500%, for Ms. Perry from 110% to 150% and for Mr. Oliver from 125% to 130%, and retained the existing 180% targets for Mr. Shoaf and Ms. Brown. TheBrown from 180% to 200% and for Ms. Perry and Mr. Oliver from 150% to 180%. Prior to 2021, the Compensation Committee hashad not made any adjustments to our NEOs' long-term incentive targets since 2018, with the exception of an increase in Mr. Oliver's long-term incentive target from 130% to 150% following his January 2020 promotion to Executive Vice President. The following table shows each NEO's long-term incentive target for 20202021 (expressed as a percent of base salary).

The Compensation Committee allocates a percentage of long-term incentive award value to performance-based awards and a percentage to awards that focus on retention and increasing ownership levels of executive officers (including our NEOs). Since 2011, the target levels of long-term incentive award value have been allocated in the following manner:

The Compensation Committee reviews and approves long-term incentive grants for each of the NEOs. The CEO develops individual grant recommendations for the other NEOs based upon the methodology described above, but both the CEO and the Compensation Committee may make adjustments to the recommended grants for such other NEOs based upon an assessment of an individual's performance and contributions to NuStar Energy. Grants to the CEO are decided solely by the Compensation Committee following the methodology described above. The Chairman of the Board makes grant recommendations for the CEO, and the Compensation Committee may make discretionary adjustments to the calculated level of long-term incentives for the CEO based upon its independent evaluation of the CEO's performance and contributions.

Performance awards are earned only upon NuStar Energy's achievement of the performance measures established by the Compensation Committee for the performance period. The Compensation Committee believes this type of incentive award strengthens the tie between each NEO's pay and our performance.

The Compensation Committee believes that, following the significant changes undertaken by NuStar Energy during 2018, the combination of these two equally weighted, objective performance measures (TUR and DCR) focuses our NEOs on both NuStar Energy's longer-term performance relative to its peer companies, as well as NuStar Energy's absolute performance against a key financial goal. To reflect NuStar Energy's performance as compared to the Compensation Comparative Group since the completion of the Merger in 2018, the Compensation Committee determined that the 20202021 TUR performance period would be

After the end of the performance period, the TUR for NuStar and each company listed in the Compensation ComparativePerformance Award Peer Group below is determined based on its total return to its unitholders or shareholders, based upon the growth in its unit or share price, as well as its cash distributions to its holders, during the performance period, and performance is ranked by quartile. The Performance Award Peer Group was approved by the Compensation Committee on July 19, 2021, prior to Meridian's updated analysis of our executive compensation programs, and it is consistent with the peer group used by EPPA in its analyses for the Compensation Committee prior to Meridian's August 2021 appointment. All of the companies in the Performance Award Peer Group also are included in the Core Group used by Meridian for its 2021 analysis of our executive compensation program.

DCR is a non-GAAP financial measure of performance derived from our financial statements. DCR was determined for this purpose by dividing Adjusted DCF (described above under "Bonus Awards—Company Performance Objectives") by the distributions applicable to common limited partners contained in NuStar Energy's 2020 budget, which was approved by the Board during the fourth quarter of 2019. As such, the DCR calculation for this performance measure did not benefit from the impact of the common unit distribution reduction during 2020.partners.

If performance falls between the benchmarks established by the Compensation Committee for the applicable performance period, the percentage vesting with respect to that performance measure during the performance period is determined through straight-line interpolation. The Compensation Committee retains the full discretion to vest up to 200% of performance awards available for vesting, regardless of the performance level attained against the performance measures established for the applicable performance period. Any performance awards not earned at target in a given performance period will be carried forward (the(referred to as Carried Forward Units)Units in the case of performance units and Carried Forward Cash Awards in the case of performance cash awards) for one additional performance period, with up to 100% of such Carried Forward Units and/or Carried Forward Cash Awards having the opportunity to vest based upon NuStar Energy's performance in the following performance period.

Performance awards vest in three annual increments (or tranches). As illustrated in the table below, one third of each of the 2018, 2019, 2020 and 20202021 performance awards was eligible to vest based upon our TUR and DCR performance measures during the 20202021 performance periods. There were noIn addition, the Carried Forward Units from the 2018 orand 2019 performance unit awards and the Carried Forward Cash Awards from the 2020 performance cash awards were eligible to vest with respect to the 20202021 performance periods.

On January 28, 2021,27, 2022, for the applicable 20202021 performance periods, the Compensation Committee determined that NuStar Energy achieved TUR performance in the firstsecond quartile for all remaining public companies inof the Compensation ComparativePerformance Award Peer Group and achieved a DCR of 1.342.0356 : 1. Accordingly, pursuant to the award terms and as set forth in the table below, the 2019, 2020 and 2021 performance awards available to vest under the applicable tranche for each of the 2018 performance unit awards, 2019 performance unit awards and 2020 performance cash awards with respect to the 20202021 performance periods vested at 93%, determined as follows:150% and the Carried Forward Units and Carried Forward Cash Awards available to vest with respect to the 2021 performance periods vested at 100% (the maximum level for Carried Forward Units and Carried Forward Cash Awards):

As described above under "Form of Performance Awards," performance unit awards are settled in common units upon vesting while performance cash awards are settled in cash, unless the Compensation Committee decides at vesting to settle the performance cash awards in the form of common units. On January 28, 2021,27, 2022, the Compensation Committee decided to settle the performance cash awards that vested with respect to 20202021 performance in the form of fully vested common units pursuant to the 2019 LTIP, consistent with the manner in which performance unit awards are settled, thus reinforcing the alignment between our NEO'sNEOs' interests and those of our unitholders. As provided in the performance cash award agreements, the number of common units used to satisfy the vested performance cash awards was determined based on the closing price of a NuStar Energy common unit on the NYSE on the January 28, 202127, 2022 vesting date. The dollar value of those units are reported in the "Non-Equity Incentive Plan Compensation" column of the Summary Compensation Table for 2020.2021.

Restricted units comprise approximately 65% of each NEO's total long-term incentive target. No units are issued at the time of grant and restricted unit awards represent the right to receive common units upon vesting. The awards are calculated from an

assumed unit value based on the average closing price of the common units for the first 10 business days of the four-week period before the committee meeting at which the awards are to be approved.

For 2020,2021, approximately 53% of our employees received a restricted unit awards.award. Restricted unit awards for our U.S. employees, including our NEOs, vest over five years in equal increments on the anniversary of the grant date, and common unit distribution equivalents are paid in cash quarterly for all unvested restricted units. Due to the continuing low unit price environment associated with the pandemic and the ongoing economic uncertainty, the number of our common units required to satisfy the calculated value of our 20202021 annual restricted unit awards increasedremained elevated as compared to the number required for the 2019 annual awards.awards, prior to the pandemic. Accordingly, to preserve NuStar Energy's cash while still maintaining relatively comparable distribution equivalent value, relatively comparable to 2019, the Compensation Committee determined that all employees receiving 20202021 annual restricted unit awards, including our NEOs, would receive distribution equivalent payments with respect to those 20202021 annual awards equal to the product of the number of restricted units granted to the employee that remain outstanding and unvested as of the record date for such quarter and 0.400.575 times the quarterly distribution declared by the Board for such quarter with respect to NuStar Energy's common units.

The 20202021 annual restricted unit awards were approved by the Compensation Committee on October 20, 2020.27, 2021. The Compensation Committee determined that the grants would be made under the 2019 LTIP, effective on November 16, 2020,2021, following the public disclosure of NuStar Energy's third quarter 20202021 results and consistent with the restricted unit grant date in previous years. The following table sets forth the number of restricted units granted to each of our NEOs in 2020.2021.

We provide only minimal perquisites to our NEOs. Each of our NEOs received federal income tax preparation services and personal liability insurance in 2020.2021. For more information on perquisites, see the Summary Compensation Table and its footnotes.

For a discussion of our Pension Plan, as well as the Excess Pension Plan, please see the narrative description accompanying the table entitled "Pension Benefits for the Year Ended December 31, 2020.2021."

Thrift Plan consists of a separate plan for purposes of Title I of ERISA. To the extent a participant's annual total compensation exceeds the compensation limits for the calendar year under Section 401(a)(17) of the Code ($285,000290,000 for 2020)2021) or a participant's annual additions under the Thrift Plan are limited by the maximum annual additions permitted under Section 415 of the Code ($57,00058,000 for 2020)2021), the participant's Excess Thrift Plan account is credited with that number of hypothetical NuStar Energy units that could have been purchased with the difference between:

Each of our NEOs participated in the Excess Thrift Plan in 2020.2021.

We initially entered into change of control severance agreements with each of our NEOs in, or prior to, 2007. The change of control severance agreements are intended to ensure the continued availability of these executives in the event of certain transactions culminating in a "change of control" as defined in the agreements. The change of control severance agreements have three-year terms and are automatically extended for one year upon each anniversary unless we give notice not to extend. If a "change of control" (as defined in the agreements) occurs during the term of an agreement, then the agreement becomes operative for a fixed three-year period. The agreements provide generally that the NEO's terms and conditions of employment (including position, location, compensation and benefits) will not be adversely changed during the three-year period after a change of control.

The agreements contain tiers of compensation and benefits based on each NEO's position. Each tier corresponds to a certain "severance multiple" used to calculate cash severance and other benefits to be provided under the agreements. Compensation and benefits under the agreements are triggered upon the occurrence of any of the following in connection with a change of control:

These triggers were designed to ensure the continued availability of these executives following a change of control, and to compensate them at appropriate levels if their employment is unfairly or prematurely terminated during the applicable term following a change of control.

The following table sets forth the severance multiple applicable to each NEO, based on his or her officer position.

None of the NEOs have employment agreements, other than the change of control severance agreements described above. As a result, in the event of a termination, retirement, death or disability that is not related to a change of control, an NEO will only receive the compensation or benefits to which he or she would be entitled under the terms of the defined contribution, defined benefit, medical or long-term incentive plans, as applicable.

Our restricted unit awards are considered "phantom" units, as they represent the right to receive our common units upon vesting. We account for restricted units expected to result in the issuance of our common units upon vesting as equity-classified awards. The restricted units granted to our U.S. employees (including our NEOs) generally vest over five years and the restricted units granted to non-employee directors generally vest over three years. We record compensation expense ratably over the vesting period based on the fair value of the units at the grant date (for U.S. employees, including our NEOs, and non-employee directors). Common unit distribution equivalents paid with respect to outstanding, unvested equity-classified restricted units reduce equity, similar to cash distributions to unitholders. Restricted units awarded to international employees are liability-classified awards that are cash-settled and measured at fair value based on the common unit price at each reporting period.

Performance awards may be granted in the form of performance units or performance cash awards. Performance awards vest in three annual increments (tranches), based upon our achievement of the performance measures established by the Compensation Committee for the applicable performance periods. Therefore, under applicable accounting standards, a tranche of performance awards is not considered "granted" until the Compensation Committee has set the performance measures for that specific tranche of the award. Performance unit awards represent the right to receive common units and are equity-classified awards. Performance unit awards are measured at the grant date fair value once the performance measures are established for a specific tranche. In addition, since performance unit awards do not receive common unit distribution equivalents, the estimated fair value of these awards does not include the per unit distributions expected to be paid to common unitholders during the vesting period. Performance cash awards are accounted for as a liability but may be settled in common units. For performance awards, we record compensation expense ratably for each vesting tranche over its service period if it is probable that the specified performance measures will be achieved. Additionally, changes in the actual or estimated outcomes that affect the quantity of performance awards expected to be converted into common units or paid in cash are recognized as a cumulative adjustment.

We believe that ownership of NuStar Energy units aligns the interests of our directors and executives with those of our unitholders. We have long emphasized and reinforced the importance of unit ownership among our executives and directors, and our BoardCompensation Committee has approved the unit ownership and retention guidelines described below.

During their service as a Board member, non-employee directors are expected to acquire and hold NuStar Energy units with an aggregate value based on a multiple of at leasttheir annual cash retainer. Following Meridian's analysis of our compensation programs, in October 2021 our Compensation Committee increased the NuStar Energy unit ownership requirement for our non-employee directors from a value equal to two times their annual cash retainer to five times their annual cash retainer. DirectorsOur non-employee directors have five years from the later of their initial election toappointment or the Boarddate the Compensation Committee approves an increase in the multiple to meet the target unit ownership guidelines, and they are expected to continuously own sufficient units to meet the guidelines, once attained. As of December 31, 2020,2021, each of our non-employee directors exceeded (or is on track to exceed within the required time period) the ownership levels set forth in the unit ownership guidelines.

Unit ownership guidelines for the officer positions set forth below are as follows:

The officers subject to the unit ownership and retention guidelines, including each of our NEOs, are expected to meet the applicable guidelines within five years of becoming subject to the guidelines, or receiving a subsequent promotion corresponding to a higher multiple in the table above or the Compensation Committee approving an increase in the applicable multiple, and are expected to continuously own sufficient units to meet the guidelines, once attained. As of December 31, 2020,2021, each of our NEOs exceeded the ownership levels set forth in the unit ownership guidelines.

For purposes of satisfying the unit ownership guidelines, the following units are considered owned:

Unexercised unit options and unvested performance unitsawards are not considered owned for purposes of satisfying the unit ownership guidelines.

We have a written policy prohibiting all members of our Board and all of our employees, including our officers, from purchasing or selling securities of NuStar Energy while in possession of material, nonpublic information or otherwise using such information for their personal benefit or in any manner that would violate applicable laws and regulations. All members of our Board, our officers and certain of our other employees also are prohibited from trading in our securities for the period beginning on the last business day of each calendar quarter through the first business day following our disclosure of our quarterly or annual financial results. Our policy also prohibits all members of our Board and all of our employees, including our officers, from purchasing, selling or writing calls, puts or options on our securities. In addition, all members of our Board, our officers and certain of our other employees must receive prior consent from our Chief Executive Officer (or, in the case of our Chief Executive Officer, from the Chair of the Audit Committee) before entering into a margin loan or other financing arrangement involving our securities.

The Compensation Committee has focused on aligning our compensation policies with the long-term interests of NuStar Energy and avoiding short-term rewards for management decisions that could pose long-term risks to NuStar Energy. As described above in "Compensation Discussion and Analysis," the primary elements of our compensation program are base salary, annual incentive bonus and long-term incentives. We believe that our compensation program appropriately balances cash with equity-based compensation and fixed compensation with short- and long-term incentives such that no single pay element would motivate unnecessary risk taking.

The following table provides a summary of compensation paid for the years ended December 31, 2021, 2020 December 31,and 2019 and December 31, 2018 to our Chief Executive Officer, Chief Financial Officer and our three other most highly compensated executive officers serving during 2020.2021. For each NEO, the table shows the NEO's current position and the amounts earned for services rendered to us in all capacities in which the NEO served during the periods presented for that NEO.presented.