We recognized a net realized investment gain totaling $1,302.3 million in 2020 related to the transfer of investments in the Closed Block individual disability reinsurance transaction. Credit losses on fixed maturity securities of $53.6 million were recognized in net realized investment gains and losses in 2020 compared to $25.3 million and $17.5 million in 2019 and 2018. We also recognized $36.6 million of impairment losses in 2020 related to certain of our home office buildings available for lease and classified as investment real estate. Also, included in net realized investment gains and losses were changes in the fair value of an embedded derivative in a modified coinsurance arrangement, which resulted in realized gains (losses) of $(17.0) million, $8.3 million, and $(15.2) million in 2020, 2019, and 2018, respectively. See Notes 3 and 4 of the "Notes to Consolidated Financial Statements" contained herein in Item 8 for further discussion. Other income is primarily comprised of fee-based service products in the Unum US segment, which include leave management services and administrative only (ASO) business, and the underlying results and associated net investment income of certain assumed blocks of individual disability reinsured business in the Closed Block segment. Overall benefits experience was unfavorable in 2020 relative to the prior periods, with a consolidated benefit ratio of 95.7 percent in 2020 compared to 80.0 percent in 2019 and 89.3 percent in 2018. Excluding the 2020 long-term care reserve increase, group pension reserve increase and impacts from the Closed Block individual disability reinsurance transaction the benefit ratio for 2020 was 80.2 percent. Excluding the 2018 long-term care reserve increase, the benefit ratio for 2018 was 80.9 percent. The underlying benefits experience for each of our operating business segments is discussed more fully in "Segment Results" contained herein in this Item 7. Commissions and the deferral of acquisition costs were lower in 2020 compared to 2019 driven primarily by lower sales in our Unum US voluntary benefits product line and Colonial Life segment. Commissions increased in 2019 compared to 2018 driven primarily by sales growth. The deferral of acquisition costs was lower during 2019 relative to 2018 due primarily to a shift in product mix that resulted in lower first-year commissions and a lower corresponding deferral of acquisition costs in the Unum US supplemental and voluntary product line. The amortization of deferred acquisition costs was generally consistent with 2019. Growth in the level of the deferred asset in our Unum US and Colonial Life segments resulted in higher amortization of deferred acquisition costs in 2019 compared to 2018. Also contributing to the increase in the amortization of deferred acquisition costs in 2019 was a higher level of policy terminations experienced in the Unum US voluntary benefits product line and the impact of the prospective unlocking for future experience relative to assumptions in certain of our Colonial life products. Interest and debt expense increased year-over-year in 2020 and 2019 due primarily to a higher level of outstanding debt. Cost related to early retirement of debt includes costs associated with the purchase and retirement of $433.1 million aggregate liquidation/principal amount of our outstanding capital and debt securities in 2019. See Note 8 of the "Notes to Consolidated Financial Statements" contained herein in Item 8 for further discussion. Other expenses, including compensation expense, increased in each of the years presented above due to operational investments in our business and growth in our fee-based service products, which was balanced with our continued focus on expense management and operating efficiencies. Included in other expenses for 2020 are costs related to an organizational design update, an impairment loss on the ROU asset related to an operating lease for office space, costs related to the Closed Block individual disability reinsurance transaction, and an increase in the provision for the allowance for expected credit losses on premium receivable balances. Our effective income tax rate for 2020 was 17.7 percent, compared to 20.4 percent in 2019 and 16.6 percent in 2018. Our 2020, 2019, and 2018 effective tax rates differed from the U.S. statutory rate of 21 percent due to favorable tax credits, with additional favorable adjustments in 2018 related to our prior year tax return. Also impacting the difference between the effective tax rate and the U.S. statutory rate in 2020 was the unfavorable impact of the U.K. tax rate increase, as well as the favorable impact related to net operating loss carryback. See Note 7 in the "Notes to Consolidated Financial Statements" contained herein in Item 8 for further discussion. 61