respectively, of these expenses were included in Cost of services, and $4.4 million and $14.0 million, respectively, of these expenses were included in Selling, general, and administrative in the Condensed Consolidated Statements of Income.
These expenses are specific to this initiative; however, the types of expenses related to this initiative are similar to expenses that we have previously incurred and can reasonably be expected to incur in the future.
Cost of Services
Cost of services primarily consists of agent commissions, which represented approximately 60% of total cost of services for both the three and six months ended June 30, 2021. Cost of services increased for the three and six months ended June 30, 2021 compared to the corresponding periods in the prior year due to increases in agent commissions in our Consumer-to-Consumer money transfer business, which generally vary with revenues, information technology costs, and bank fees associated with digital transactions.
Selling, General, and Administrative
Selling, general, and administrative expenses increased for the three and six months ended June 30, 2021 compared to the corresponding periods in the prior year due to increases in employee-related expenses, including incentive compensation, marketing costs, and costs related to strategic initiatives, including for the review of mergers, acquisitions, and divestitures, partially offset by a reduction in restructuring-related expenses. The increase in employee-related expenses was also a result of reduced hiring that we implemented in response to COVID-19 in the prior year periods. For the six months ended June 30, 2021 compared to the corresponding period in the prior year, these increases were partially offset by fluctuations between the United States dollar and foreign currencies.
Total Other Income/(Expense), Net
Total other income/(expense), net during the three and six months ended June 30, 2021 when compared to the corresponding periods in the prior year benefited from a $47.9 million gain recorded from the sale of a substantial majority of the shares we held as a minority investor in a private company for cash proceeds of $50.9 million and a reduction in interest expense driven by lower average debt balances outstanding and a lower weighted-average interest rate on our outstanding debt. These benefits were partially offset by costs associated with the repayment of our 3.6% unsecured notes due in 2022.
On July 22, 2021, our Board of Directors approved a plan to terminate and settle our frozen defined benefit pension plan. Our defined benefit pension plan was in an overfunded position as of June 30, 2021 and December 31, 2020, which prompted us to explore other options with this retirement plan. Upon termination and settlement, which is expected in the fourth quarter of 2021 and subject to required notices, filings, and reviews, the pre-tax balance in Accumulated other comprehensive loss associated with the defined benefit pension plan, along with any related costs of the settlement, will be recorded as a component of Total other income/(expense), net, with the related income tax effects recorded in Provision for income taxes, in the Condensed Consolidated Statements of Income.
Income Taxes
Our provision for income taxes for the three and six months ended June 30, 2021 and 2020 is based on the estimated annual effective tax rate, in addition to discrete items. Our effective tax rates on pre-tax income were 14.5% and 16.2% for the three months ended June 30, 2021 and 2020, respectively and 12.7% and 14.3% for the six months ended June 30, 2021 and 2020, respectively. The decrease in our effective tax rate for the three and six months ended June 30, 2021 compared to the prior periods was primarily due to changes in pre-tax earnings, including differences in the composition between high-tax and low-tax jurisdictions. The decrease in our effective tax rate for the six months ended June 30, 2021 compared to the corresponding period in the prior year was also impacted by increased discrete tax benefits in the current period.
We have established contingency reserves for a variety of material, known tax exposures. As of June 30, 2021, the total amount of tax contingency reserves was $311.9 million, including accrued interest and penalties, net of related items.