In the first quarter of 2003, we leased additional space in Rye Brook, New York, from an unaffiliated company. Rye Brook is approximately 30 miles north of Manhattan. Our administrative, accounting and information technology staffs and certain executive officers are now located at our Rye Brook, New York office. Our lease for this space terminates in February 2013.
Our revenue is primarily comprised of premiums, commission and investment income. Our insurance company subsidiaries derive their premiums primarily from business written by the Navigators Agencies. The Lloyd's Operations derive their premiums from business written by NUAL. The Navigators Agencies and NUAL receive commissions and, in some cases, profit commissions and service fees on the business produced on behalf of our insurance company subsidiaries and others.
Our most critical accounting policies involve the reporting of the reserves for losses and LAE (including losses that have occurred but were not reported to us by the financial reporting date), reinsurance recoverables, written and unearned premium, the recoverability of deferred tax assets, the impairment of invested assets, accounting for Lloyd's results and the translation of foreign currencies.
Marine Premium. The 2005 business consists of 33% marine liability, 18% offshore energy, 12% transport, 10% cargo, 8% blue water hull with the remainder in several other marine related classes of business. The marine gross written premium for 2005 increased 11.1% compared to 2004 due to growth across several lines of business including cargo, offshore energy and liability. During 2005, we also began to insure customs bonds. The average marine renewal premium rates during 2005 were relatively flat over the first nine months and then increased approximately 2.1% in the fourth quarter following Hurricanes Katrina and Rita resulting in an approximate 1.5% average increase for the 2005 year. The 2004 marine gross written premium increased 7.1% principally due to the addition of protection and indemnity business written by our UK Branch commencing early in the year coupled with the 4.7% average increase in renewal premium rates during the year. Primary marine protection and indemnity (P&I) business complements our marine liability business which is generally written above the primary layer on an excess basis. The rate increases in the marine business slowed in 2004 compared to the prior two years. Rate increases in 2003 averaged approximately 13%. Navigators Insurance Company obtains its marine business through participation in the marine pool managed by the Navigators Agencies. Its participation in the marine pool was 85% in 2005 and 80% in both 2004 and 2003. Commencing in 2006, the marine pool has been eliminated and, therefore, all of the marine business generated by the Navigators Agencies will be exclusively for Navigators Insurance Company.
Other Income/(Expense). Other income/(expense) for 2005, 2004 and 2003 consisted principally of both foreign exchange gains and (losses) of $1,792,000, $(1,310,000) and $612,000, respectively, primarily related to the Lloyd's Operations, and of inspection fees of $1,041,000, $873,000 and $750,000, respectively, related to the specialty insurance business.
During 2004, ultimate loss ratios for our Lloyd's Operations were reduced for the 2003 and 2002 underwriting years for cargo, hull and the assumed marine excess of loss business mostly as a result of lower than expected claims activity coupled with the recognition of underwriting improvements for the business written for the 2003 underwriting year. Such factors were the principal reasons for the ultimate loss ratio reductions which occurred throughout the 2004 calendar year contributing to the $6.6 million prior year savings recorded by our Lloyd's Operations and the $2.2 million prior year savings recorded by our Insurance Companies for the business assumed from Lloyd's.
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a large portion of their reinsurance participation for the 2003 year of account to Navigators Insurance Company. A summary of the effect of the 2004 RITC transaction on our financial statements is as follows:
At December 31, 2005, the weighted average rating of our fixed maturity investments was "AA" by Standard & Poor's and "Aa" by Moody's. We believe that we have no significant exposure to credit risk since the fixed maturity investment portfolio consists of investment-grade bonds. At December 31, 2005, our portfolio had an average maturity of 5.2 years and a duration of 3.8 years. Management continually monitors the composition and cash flow of the investment portfolio in order to maintain the appropriate levels of liquidity to ensure our ability to satisfy claims. No impairment losses were incurred in 2005, 2004 or 2003. As of December 31, 2005 and 2004, all fixed maturity securities and equity securities held by us were classified as available-for-sale.
The credit facility is collateralized by all of the common stock of Navigators Insurance Company. The credit agreement contains covenants common to transactions of this type, including restrictions on indebtedness and liens, limitations on mergers and the sale of assets, maintaining certain consolidated tangible net worth, statutory surplus and other financial ratios. Cash dividends to shareholders are limited to $2.5 million per year. No dividends have been declared or paid and we were in compliance with all covenants through December 31, 2005.
At December 31, 2005, our consolidated stockholders' equity was $470.2 million compared to $328.6 million at December 31, 2004. The increase was primarily due to the $123.8 million of net proceeds from the October 2005 equity offering and, to a lesser extent, the 2005 year net income of $23.6 million offset by $8.3 million of after-tax unrealized loss for the year ended December 31, 2005.
We primarily rely upon dividends from our subsidiaries to meet our holding company obligations. The dividends have historically come primarily from Navigators Insurance Company. At December 31, 2005, the maximum amount available for the payment of dividends by Navigators Insurance Company during 2006 without prior regulatory approval was $35,648,000. During 2005, 2004 and 2003, Navigators Insurance Company paid dividends to us of $3 million, $6 million and $6 million, respectively.