In 2013, we adopted plan amendments which froze participation and benefit accruals in our defined benefit pension plans in the U.S. and U.K., effective December 31, 2013 for the U.S. plans and June 30, 2014 for the U.K. plan. As a result of these plan amendments we recognized a net before-tax curtailment gain of $3.0 million during 2013. Because the amendments eliminated all future service accruals subsequent to the effective dates of the amendments, we were also required to remeasure the benefit obligations of our pension plans, which decreased our net pension liability approximately $330 million during 2013, with a corresponding increase in other comprehensive income, less applicable income tax of approximately $115 million. Concurrent with our amendments to our defined benefit pension plans, we adopted amendments to increase the benefits under our defined contribution plans commensurate with the effective dates of the pension plan amendments.
The fair value of plan assets in our U.K. pension plan was £157.0 million at December 31, 2015, compared to £158.1 million at December 31, 2014. The U.K. pension plan was in an overfunded position of £18.8 million and £12.4 million at December 31, 2015 and 2014, respectively.
The consolidated benefit ratio was 83.9 percent in 2015 compared to 93.8 percent in 2014 and 86.5 percent in 2013. Excluding the 2014 and 2013 reserve adjustments, the benefit ratios for 2014 and 2013 were 84.8 percent and 86.4 percent, respectively. The underlying benefits experience for each of our principal operating business segments is discussed more fully in "Segment Results" as follows.
Commissions and the deferral of acquisition costs were higher in 2015 relative to 2014 due to sales growth and the corresponding increase in deferrable expenses. The amortization of deferred acquisition costs increased in 2015 relative to 2014 due to growth in the level of the deferred asset. The growth in premium income during 2015 more than offset the growth in other expenses related to continued investment in the growth of our business, resulting in a decline in the other expense ratio compared to 2014.
Benefits experience for the individual disability product line in 2015 was generally consistent with 2014. Benefits experience for voluntary benefits in 2015 was favorable compared to 2014 due primarily to improved claim experience in our disability product line and a release of active life reserves in the critical illness product line resulting from a higher level of policy terminations relative to the prior year.
Sales of our group products increased in 2014 relative to 2013 in both the core and large case market segments for new and existing customer accounts. The sales mix in the group market sector for 2014 was approximately 66 percent core market and 34 percent large case market, generally consistent with the level of 2013.
Group life sales within the core market segment were higher in 2014 compared to 2013 for both new and existing customers. Group life sales in the large case market declined in 2014 relative to 2013 due to decreased sales to existing customers, partially offset by higher sales to new customers.
Shown below are financial results and key performance indicators for the Colonial Life segment.
Interest and other expenses were higher in 2014 compared to 2013 due to the costs related to the 2014 early retirement of debt and due to increased interest expense on debt, partially offset by a higher level of retirement-related costs allocated from Corporate to our other segments.
The amortization of value of business acquired, which is included in other expenses in the consolidated statements of income, was $4.6 million, $3.5 million, and $4.5 million for the years ended December 31, 2015, 2014, and 2013, respectively. We periodically review the carrying amount of value of business acquired using the same methods used to evaluate deferred acquisition costs.
Transfers of assets between Level 1 and Level 2 are as follows:
Certain of our U.S. insurance subsidiaries are members of regional FHLBs. Membership, which requires that we purchase a minimum amount of FHLB common stock on which we receive dividends, provides access to low-cost funding. As of December 31, 2015, we owned $30.9 million of FHLB common stock and had obtained $350.0 million in advances from the regional FHLBs for the purpose of purchasing fixed maturity securities. As of December 31, 2015, the carrying value of fixed maturity securities and commercial mortgage loans posted as collateral to the regional FHLBs was $317.2 million and $96.0 million, respectively. Additional common stock purchases may be required, based on the amount of funds we borrow from the FHLBs.
The following table provides the changes recognized in other comprehensive income for the years ended December 31, 2015 and 2014.
Alternative investments are valued based on the NAV of the underlying holdings in a period ranging from one month to one quarter in arrears. We evaluate the need for adjustments to the NAV based on market conditions and discussions with fund managers in the period subsequent to the valuation date and prior to issuance of the financial statements. We made no adjustments to the NAV for 2015 or 2014. The private equity direct investments and private equity funds of funds generally cannot be redeemed by investors, and distributions are received following the maturity of the underlying assets. It is estimated that these underlying assets will begin to mature between five and eight years from the date of initial investment. We have assigned a Level 3 classification to the private equity direct investments and private equity funds of funds due to the redemption restrictions on the investments. Redemptions on the hedge funds of funds can be made on either a quarterly or bi-annual basis, depending on the fund, with prior notice of at least 90 calendar days. Because of these redemption restrictions, we have classified the hedge funds of funds as Level 3.
All outstanding stock options at December 31, 2015 are expected to vest. Stock options vest over a one to three-year service period, beginning at the date of grant, and the compensation cost is recognized ratably during the vesting period. Compensation cost for stock options subject to accelerated vesting at the date of retirement eligibility is recognized over the implicit service period.
Cash received under all share-based payment arrangements for the years ended December 31, 2015, 2014, and 2013 was $6.4 million, $12.3 million, and $11.4 million, respectively.
Fairwind, which is domiciled in the State of Vermont, is required to follow GAAP in accordance with Vermont reporting requirements for pure captive insurance companies, unless the commissioner permits the use of some other basis of accounting. Fairwind has permission from Vermont to follow accounting practices that are generally consistent with current NAIC statutory accounting principles for its insurance reserves and invested assets supporting reserves. All other assets and liabilities are accounted for in accordance with GAAP, as prescribed by Vermont, which allows for the full recognition of deferred tax assets which are more likely than not to be realized. Statutory accounting principles have a stricter limitation for the recognition of deferred tax assets. The impact of following the prescribed and permitted practices of Vermont rather than statutory accounting principles prescribed by the NAIC resulted in higher capital and surplus for Fairwind of approximately $208 million and $200 million as of December 31, 2015 and 2014, respectively. Northwind Re has no material state prescribed accounting practices that differ from statutory accounting principles prescribed by the NAIC.