Assumed premiums written increased $1.9 million in 2015 as compared to 2014 due the addition of one new program to our portfolio. The new assumed program is for international catastrophes (excluding the United States) with the largest exposure to European wind perils. In 2015, we also renewed our participation in all of our assumed programs.
The property and casualty insurance segment experienced $40.4 million of favorable development in our net reserves for prior accident years for the year ended December 31, 2015. Three lines in aggregate accounted for a majority of the favorable development. The largest single contributor was long-tail liability with $23.0 million of favorable development followed by workers' compensation with $22.1 million of favorable development and auto physical damage with $4.4 million of favorable development for the year ended December 31, 2015. The favorable development is attributable to reductions in reserves for reported claims as well as reductions in required reserves for incurred but not reported claims combined with continued successful management of litigation expenses. These reserve decreases were more than sufficient to offset claim payments. The favorable development was partially offset by adverse development, the majority coming from three lines which included property with $5.6 million of adverse development from an increase in severity and frequency of losses, assumed reinsurance with $8.1 million of adverse development due to prior year development of catastrophe losses and commercial auto liability with $2.8 million of adverse development due to an increase in frequency of losses in the year ended December 31, 2015. No other single line of business contributed a significant portion of the total development.
In 2016, the change in the the loss ratio was primarily due to salvage and subrogation received in the second quarter of 2016. In 2015, the loss ratio increased slightly as compared to 2014 due to a single large claim incurred in the first quarter of 2015.
In 2016, 80.6 percent of our gross investment income originated from interest on fixed maturities, compared to 86.0 percent and 88.3 percent in 2015 and 2014, respectively.
The following table details our annualized yield on average invested assets for 2016, 2015 and 2014, which is based on our invested assets (including money market accounts) at the beginning and end of the year divided by net investment income:
Cash outflows may be variable because of the uncertainty regarding settlement dates for losses. In addition, the timing and amount of individual catastrophe losses are inherently unpredictable and could increase our liquidity requirements. The timing and amount of reinsurance recoveries may be affected by reinsurer solvency and reinsurance coverage disputes.
We invest funds required for short-term cash needs primarily in money market accounts, which are classified as cash equivalents. At December 31, 2016, our cash and cash equivalents included $16.8 million related to these money market accounts, compared to $20.8 million at December 31, 2015.
Our cash outflows for investment purchases totaled $655.9 million in 2016, compared to $701.0 million and $618.4 million for the same period in 2015 and 2014, respectively.
We record an asset for certain costs of underwriting new business, primarily commissions, premium taxes and variable underwriting and policy issue expenses that have been deferred. The amount of underwriting compensation expense eligible for deferral is based on time studies and a ratio of success in policy placement. At December 31, 2016 and 2015, our DAC asset was $93.4 million and $90.5 million, respectively.
For traditional life insurance policies, DAC is amortized to income over the premium-paying period in proportion to the ratio of the expected annual premium revenue to the expected total premium revenue. Expected premium revenue and gross profits are based on the same mortality and withdrawal assumptions used in determining future policy benefits. These assumptions are not revised after policy issuance unless the recorded DAC asset is deemed to be unrecoverable from future expected profits.
For non-traditional life insurance policies, DAC is amortized over the anticipated terms in proportion to the ratio of the expected annual gross profits to the total expected gross profits. Changes in the amount or timing of expected gross profits result in adjustments to the cumulative amortization of these costs. The effect on amortization of DAC for revisions to estimated gross profits is reported in earnings in the period the estimated gross profits are revised.
In March 2016, the FASB issued new guidance on the accounting for share-based payments. The new guidance was issued to simplify the accounting of share-based payments, specifically in the areas of income taxes, classification on the balance sheets as liabilities or equity and classification in the cash flow statement. The new guidance is effective for annual periods beginning after December 15, 2016 and interim periods within those years. The Company adopted the new guidance as of January 1, 2017. The new guidance will result in classification changes between the financing and operating section of the Statement of Cash Flow. The new guidance will also result in additional tax expense or net income, but will vary depending on the number of stock options granted and exercised.
Net investment income for the years ended December 31, 2016, 2015 and 2014, is comprised of the following:
United Life purchases reinsurance to limit the dollar amount of any one risk of loss. Our retention on standard individual life cases is $300. Our accidental death benefit rider on an individual policy is reinsured at 100 percent, up to a maximum benefit of $250. Our group coverage, both life and accidental death and dismemberment, is reinsured at 50.0 percent. Catastrophe excess reinsurance coverage applies when three or more insureds die in a catastrophic accident. For catastrophe excess claims, we retain the first $1,000 of ultimate net loss and the reinsurer agrees to indemnify us for the excess up to a maximum of $5,000. We supplement this coverage when appropriate with "known concentration" coverage. Known concentration coverage is typically tied to a specific event and time period, with a threshold of a minimum number of lives involved in the event, minimum event deductible (stated retention limit) and a maximum payout.
We also offer a health and dental benefit plan to all of our eligible employees and retirees that consists of two programs: (1) the self-funded employee health and dental benefit plan and (2) the self-funded (pre-65) and fully-funded (post-65) retiree health and dental benefit plan (the "post-retirement benefit plan"). Effective January 1, 2017, there was a plan amendment, which included the following changes: eliminated the pre-65 retirement plan with a $500 hundred dollar deductible; for retirements after January 1, 2017, the retiree will pay 50 percent of the lower cost supplemental plan if they are 65 or older and 100 percent of the premium if less than 65; and removed spousal coverage after the death of the participant. The financial impact of these changes are reflected in accumulated other comprehensive income at December 31, 2016.
Life insurance in force, before ceded reinsurance, totaled $5,314,548 and $5,491,932 as of December 31, 2016 and 2015, respectively. Traditional life insurance products represented 73.0 percent and 68.5 percent of our insurance in-force at December 31, 2016 and 2015, respectively. Universal life insurance represented 26.6 percent and 26.3 percent of insurance in force at December 31, 2016 and 2015, respectively.