We are currently in the midst of an unprecedented period of low interest rates. In response to this persistent low interest rate environment, we have been reducing policyholder crediting rates for new annuities and existing annuities since the fourth quarter of 2011. Spread results for 2014, 2013 and 2012 reflect the benefit from these reductions; however, the reductions in cost of money were offset by continued lower yields available on investments including those purchased with the reinvestment of proceeds from calls of callable bonds in our investment portfolio. In 2014, we initiated additional renewal crediting rate reductions for policies issued prior to October 8, 2011. Some of the policies included in these rate reductions will not receive the latest adjustment until their 2015 policy anniversary.
The increases in annuity product charges were primarily attributable to increases in fees assessed for lifetime income benefit riders due to a larger volume of business in force subject to the fee. See Interest sensitive and index product benefits below for corresponding expense recognized on lifetime income benefit riders. Surrender charges decreased in 2014 because the 2013 amount included surrender charges of $4.7 million deducted from California policyholders surrendering their policies as a condition of receiving certain benefits in a national class action lawsuit settlement. The increase in surrender charges in 2013 was primarily attributable to the $4.7 million amount associated with the class action lawsuit settlement.
The change in fair value of the fixed index annuity embedded derivatives resulted from (i) changes in the expected index credits on the next policy anniversary dates, which are related to the change in fair value of the call options acquired to fund those index credits discussed above in Change in fair value of derivatives; (ii) changes in discount rates used in estimating our embedded derivative liabilities; and (iii) the growth in the host component of the policy liability. See Critical Accounting Policies-Policy Liabilities for Fixed Index Annuities. The primary reasons for the increase in the change in fair value of the fixed index annuity embedded derivatives for 2014 were decreases in the discount rates used in estimating our embedded derivative liabilities, offset by decreases in the expected index credits resulting from decreases in the fair value of the call options acquired to fund those index credits. The primary reason for the decrease in the change in fair value of the fixed index annuity embedded derivatives in 2013 was an increase in the discount rates used in estimating our embedded derivative liabilities. The primary reasons for the increase in the change in fair value of the fixed index annuity embedded derivatives during 2012 were increases in the expected index credits that resulted from increases in the fair value of the call options acquired to fund these index credits and decreases in the discount rates used in estimating our embedded derivative liabilities. The discount rates used in estimating our embedded derivative liabilities fluctuate from year to year based on changes in the general level of interest rates. See Net income above for discussion of the impact of assumption changes for the fixed index annuity embedded derivatives in 2014.
During 2014 and 2013, we received $0.5 billion and $1.1 billion, respectively, in net redemption proceeds related to calls of our callable United States Government sponsored agency securities. The proceeds from these redemptions have been reinvested primarily in corporate securities, residential and commercial mortgage backed securities and United States Government sponsored agencies classified as available for sale. We remain committed to maintaining a high quality investment portfolio with low credit risk. At December 31, 2014, 33% of our fixed income securities have call features, of which 0.6% ($0.2 billion) were subject to call redemption and another 4% ($1.2 billion) will become subject to call redemption during 2015.
The transfer of funds by American Equity Life is also restricted by a covenant in our line of credit agreement which requires American Equity Life to maintain a minimum risk-based capital ratio of 275% and a minimum level of statutory surplus equal to the sum of 1) 80% of statutory surplus at September 30, 2013, 2) 50% of the statutory net income for each fiscal quarter ending after September 30, 2013, and 3) 50% of all capital contributed to American Equity Life after September 30, 2013. American Equity Life's risk-based capital ratio was 372% at December 31, 2014. Under this agreement we are also required to maintain a maximum ratio of adjusted debt to total adjusted capital of 0.35.