Equity available to preferred stockholders is equal to the redemption value of outstanding preferred stock plus share dividends declared but not yet issued.
Over these years competition has increased significantly within the fixed index annuity market. While we continue to be in the top three companies for sales of fixed index annuities within the independent agent channel, new entrants into the market have expanded the overall market through other distribution channels and our overall market share has declined from second in 2016 to fifth for the nine-months ended September 30, 2019 according to Wink's Sales and Market Report published by Wink, Inc. We attribute our leading position to our attractive product offerings, our consistent presence in the fixed index annuity market, our continued strong relationships with and excellent service provided to our distribution partners, the increased attractiveness of safe money products in volatile markets and lower interest rates on competing products such as bank certificates of deposit.
We periodically revise the key assumptions used in the calculation of amortization of deferred policy acquisition costs and deferred sales inducements retrospectively through an unlocking process when estimates of current or future gross profits (including the impact of realized investment gains and losses) to be realized from a group of products are revised. In addition, we periodically revise the assumptions used in determining the liability for lifetime income benefit riders and the embedded derivative component of our fixed index annuity policy benefit reserves as experience develops that is different from our assumptions.
Lower lapse assumptions result in an expectation that more policies will remain in force than previously anticipated which results in a greater amount of benefit payments in excess of account value and the need for a greater liability for lifetime income benefit riders. The decrease in lapse rate assumptions also results in policies being in force for a longer period of time and an increase in expected gross profits as compared to previous estimates. The higher level of expected future gross profits results in an increase in the balances of deferred policy acquisition costs and deferred sales inducements.
We have a policy and process to identify securities in our investment portfolio for which we should recognize impairments. See Critical Accounting Policies-Evaluation of Other Than Temporary Impairments.
See Note 10 to our audited consolidated financial statements for additional information concerning our subordinated debentures payable to, and the preferred securities issued by, our subsidiary trusts.
On November 21, 2019 we issued $400 million of 5.95% fixed-rate reset non-cumulative preferred stock and received net proceeds of $388.9 million. We used a portion of the proceeds to redeem $165 million of our floating rate subordinated debentures in the fourth quarter of 2019 and the first quarter of 2020 and will have $225 million of net proceeds available for general corporate purposes.
Statutory accounting practices prescribed or permitted for our life subsidiaries differ in many respects from those governing the preparation of financial statements under GAAP. Accordingly, statutory operating results and statutory capital and surplus may differ substantially from amounts reported in the GAAP basis financial statements for comparable items. Information as to statutory capital and surplus and statutory net income for our life subsidiaries as of December 31, 2019 and 2018 and for the years ended December 31, 2019, 2018 and 2017 is included in Note 12 to our audited consolidated financial statements.
Our fixed maturity securities classified as available for sale are reported at fair value. Unrealized gains and losses, if any, on these securities are included directly in stockholders' equity as a component of accumulated other comprehensive income (loss), net of income taxes and certain adjustments for assumed changes in amortization of deferred policy acquisition costs and deferred sales inducements. Unrealized gains and losses represent the difference between the amortized cost or cost basis and the fair value of these investments. We use significant judgment within the process used to determine fair value of these investments.