A summary of gross premiums written in 2015 compared with 2014 by line of business within each business segment follows:
Revenues from Wholly-Owned Investees. Revenues from wholly-owned investees were derived from aviation-related businesses that provide services to aviation markets, including (i) the distribution, manufacturing, repair and overhaul of aircraft parts and components, (ii) the sale of new and used aircraft, and (iii) avionics, fuel, maintenance, storage and charter services. Revenues from wholly-owned investees increased to $421 million in 2015 from $410 million in 2014.
Net investment income increased 10% to $601 million in 2014 from $544 million in 2013 primarily due to an increase in income from investment funds, including aviation and rail equipment funds, real estate funds and energy funds. Investment funds are reported on a one quarter lag. The average annualized yield for fixed maturity securities declined to 3.4% from 3.5% due to lower long-term reinvestment yields available in the market. The effective duration of the fixed maturity portfolio was 3.2 years at December 31, 2014 compared with 3.3 years at December 31, 2013. Average invested assets, at cost (including cash and cash equivalents), were $15.6 billion in 2014 and $14.8 billion in 2013.
Expenses from Wholly-Owned Investees. Expenses from wholly-owned investees represent costs associated with aviation-related businesses that include (i) cost of goods sold related to aircraft and products sold and services provided, and (ii) general and administrative expenses. Expenses from wholly-owned investees were $401 million in 2014 compared to $389 million in 2013, primarily due to start-up costs from a new business operation.
Contracts that do not meet the risk transfer requirements of GAAP are accounted for using the deposit accounting method. Under this method, an asset or liability is recognized at the inception of the contract based on consideration paid or received. The amount of the deposit asset or liability is adjusted at subsequent reporting dates using the interest method with a corresponding credit or charge to interest income or expense. Deposit liabilities for assumed reinsurance contracts were $54 million and $68 million at December 31, 2015 and 2014, respectively.
At December 31, 2015 and 2014, there were no investments, other than investments in United States government and government agency securities, which exceeded 10% of common stockholders’ equity. At December 31, 2015, investments with a carrying value of $1,201 million were on deposit in custodial or trust accounts, of which $963 million was on deposit with state insurance departments, $182 million was on deposit in support of the Company’s underwriting activities at Lloyd’s, $41 million was on deposit as security for reinsurance clients and $15 million was on deposit as security for letters of credit issued in support of the Company’s reinsurance operations.
The following tables present the assets and liabilities measured at fair value on a recurring basis as of December 31, 2015 and 2014 by level:
Claims occurring during the current year are net of loss reserve discounts of $20,357,000, $21,306,000, and $22,680,000 in 2015, 2014 and 2013, respectively.
In 2014, the Company entered into a commutation agreement that resulted in a reduction in prior year workers' compensation reserves of $30 million on an undiscounted basis and $12 million on a discounted basis.
The Company’s insurance subsidiaries are restricted by law as to the amount of dividends they may pay without the approval of regulatory authorities. The Company’s lead insurer, Berkley Insurance Company (BIC), directly or indirectly owns all of the Company’s other insurance companies. During 2016, the maximum amount of dividends that can be paid by BIC without such approval is approximately $684 million.
Summary financial information about the Company’s reporting segments is presented in the following table. Income (loss) before income taxes by segment includes allocated investment income. Identifiable assets by segment are those assets used in or allocated to the operation of each segment.