In September 2015, we acquired 100 percent of the common shares and voting interests in National Dental Plan Limited and associated companies (National Dental) for a total cash purchase price of £35.9 million or $54.3 million. National Dental, a leading provider of dental insurance in the U.K. workplace, is reported in our Unum UK segment as part of our supplemental product line. The acquisition of National Dental extends our market reach, broadening our employee benefit offerings in the U.K. This acquisition, the results of which are included in our financial results and sales for the period subsequent to the date of acquisition, did not have a material impact on revenue, operating results, or sales for 2015. See Note 13 of the "Notes to Consolidated Financial Statements" contained herein in Item 8 for further details on the acquisition.
During the fourth quarter of 2013, we completed our assessment of benefits which we estimate will be paid under this initiative, and as such, established additional reserves for payment of these benefits. Claim reserves were increased $49.1 million for Unum US group life, $26.3 million for Unum US voluntary life, and $20.1 million for Colonial Life voluntary life, for a total reserve increase of $95.5 million. These reserve adjustments decreased 2013 net income $62.1 million.
Risk-free interest rates of 1.76 percent for five-year maturities to 3.02 percent for 30-year maturities were derived from the December 31, 2015 yield curve for U.S. Treasury Bonds with similar maturities. This compares to interest rates of 1.65 percent for five-year maturities to 2.75 percent for 30-year maturities used at December 31, 2014.
The comparability of our financial results between years is affected by the fluctuation in the British pound sterling to dollar exchange rate. The functional currency of our U.K. operations is the British pound sterling. In periods when the pound weakens relative to the preceding period, translating pounds into dollars decreases current period results relative to the prior period. In periods when the pound strengthens, translating pounds into dollars increases current period results relative to the prior period. Our weighted average pound/dollar exchange rate was 1.528, 1.646, and 1.566 for years ended 2015, 2014, and 2013, respectively. If the 2014 and 2013 results for our U.K. operations had been translated at the lower exchange rate of 2015, our operating revenue by segment in 2014 and 2013 would have been lower by approximately $54.9 million and $16.2 million, respectively, and our operating income in 2014 and 2013 would have been lower by approximately $10.5 million and $3.2 million, respectively. However, it is important to distinguish between translating and converting foreign currency. Except for a limited number of transactions, we do not actually convert pounds into dollars. As a result, we view foreign currency translation as a financial reporting item and not a reflection of operations or profitability in the U.K.
Benefits experience was favorable in 2015 compared to 2014 due to favorable incurred benefits in the accident, sickness, and disability product line and the release of active life reserves in the cancer and critical illness product lines related to policy terminations.
Derivative instruments may be used to replicate permitted asset classes, hedge interest rate risk, credit risk, and foreign currency risk, and match liability duration and cash flows consistent with the plan reviewed by the risk and finance committee of Unum Group's board of directors and approved by the boards of directors of our insurance subsidiaries.
In determining when a decline in fair value below amortized cost of a fixed maturity security is other than temporary, we evaluate available information, both positive and negative, in reaching our conclusions. In particular, we consider the strength of the issuer's balance sheet, its debt obligations and near-term funding requirements, cash flow and liquidity, the profitability of its core businesses, the availability of marketable assets which could be sold to increase liquidity, its industry fundamentals and regulatory environment, and its access to capital markets. Although all available and applicable factors are considered in our analysis, our expectation of recovering the entire amortized cost basis of the security, whether we intend to sell the security, whether it is more likely than not that we will be required to sell the security before recovery of its amortized cost, and whether the security is current on principal and interest payments are the most critical factors in determining whether impairments are other than temporary. The significance of the decline in value and the length of time during which there has been a significant decline are also important factors, but we generally do not record an impairment loss based solely on these two factors, since often other more relevant factors will impact our evaluation of a security.
This update eliminates the requirement to categorize within the fair value hierarchy table investments whose fair value is measured at net asset value using the practical expedient. Instead, entities will be required to disclose the fair value of these investments so that financial statement users can reconcile amounts reported in the fair value hierarchy table to the amounts reported on the consolidated balance sheets. The guidance is to be applied retrospectively.
Represents basis point adjustments for changes in benchmark spreads associated with various ratings categories
At December 31, 2015, we had commitments of $67.0 million to fund certain commercial mortgage loans, the amount of which may or may not be funded.
At December 31, 2015 and 2014, the annual rate of increase in the per capita cost of covered postretirement health care benefits assumed for the next calendar year is 7.50 percent for each year for benefits payable to both retirees prior to Medicare eligibility as well as Medicare eligible retirees. The rate is assumed to change gradually to 5.00 percent by 2021 for measurement at December 31, 2015 and remain at that level thereafter.
We made no contributions to our U.K. plan during 2015, nor do we expect to make any contributions in 2016, either voluntary or those required to meet the minimum funding requirements under U.K. legislation.
We report goodwill in our Unum US segment and in our Unum UK segment, which are the segments expected to benefit from the originating business combinations. At December 31, 2015 and 2014, goodwill was $230.9 million and $198.7 million, respectively, with $187.6 million attributable to Unum US in each year and the remainder attributable to Unum UK.
In May 2013, a purported class action complaint was filed in the Superior Court of California, County of Los Angeles. The plaintiff sought to represent a class of California insureds who were issued long-term care policies containing an inflation protection feature. The plaintiff alleged we incorrectly administered the inflation protection feature, resulting in an underpayment of benefits. The complaint made allegations against us for breach of contract, bad faith, fraud, violation of Business and Professions Code 17200, and injunctive relief. We removed the case to the United States District Court for the Central District of California, and plaintiff filed an amended complaint on behalf of a nationwide class of insureds who were issued long-term care policies containing an inflation protection feature. After we answered the complaint, the court permitted the plaintiff to file another amended complaint entitled Michael Don, Executor of The Estate of Ruben Don, Leroy Little, by and through his Guardian ad Litem Tamara Pelham, and Carolyn Little v. Unum Group, and Unum Life Insurance Company of
America containing similar allegations. In April 2015, we again answered the complaint. The plaintiffs filed a motion seeking certification of five subclasses, and we filed our opposition. In February 2016, the plaintiffs filed a motion for preliminary approval of settlement for a class of certain insureds issued long-term care policies containing an inflation protection feature as well as certain insureds who requested copies of their long-term care policies. The court has not yet ruled on this motion. We accrued an estimated loss contingency in 2015, the amount of which was immaterial to our consolidated financial position and results of operations.
The following is a summary of our unaudited quarterly results of operations for 2015 and 2014: