catastrophe losses in the year ended December 31, 2009. Total net written premiums decreased 35.2% in the year ended December 31, 2010 to $1,236.3 million, compared to $1,906.7 million in the year ended December 31, 2009. The decrease in net written premiums was due primarily to the Commercial Lines Transaction and the Personal Lines Transaction, both of which are described below.
Our income tax expense related to pre-tax income for the years ended December 31, 2010 and 2009 represented effective tax rates of 6.7% and 24.7%, respectively. The effective tax rate for the year ended December 31, 2010 was lower than the U.S. statutory rate of 35% due to income generated in jurisdictions other than the United States and recognition of a deferred tax asset for a higher tax basis and deconsolidation of the companies sold as part of the Personal Lines Transaction, partially offset by an increase in the valuation allowance for insurance reciprocals. The effective tax rate for the year ended December 31, 2009 was lower than the U.S. statutory rate of 35% primarily due to income generated in jurisdictions other than the United States and the settlement of federal income tax audits for 2003 and 2004.
Our comprehensive income attributable to OneBeacon's common shareholders was $360.8 million in the year ended December 31, 2009, compared to a comprehensive loss attributable to OneBeacon's common shareholders of $408.2 million in the year ended December 31, 2008. Change in other comprehensive income and loss items in the year ended December 31, 2009 included the impact of a $12.1 million after tax increase in our pension plans primarily related to an increase in the over-funded status of our qualified pension plan driven by investment results. Change in other comprehensive income and loss items in the year ended December 31, 2009 also included a $7.4 million pre-tax ($4.8 million after tax) increase resulting from the settlement of our interest rate swap relating to the mortgage note. Change in other comprehensive income and loss items in the year ended December 31, 2008 included the impact of a $19.5 million after tax decrease in our pension plans primarily related to a decrease in the over-funded status of our qualified pension plan driven by investment results and a $5.7 million after tax decrease in our interest rate swap related to the mortgage note. Net income attributable to OneBeacon's common shareholders was $342.0 million in the year ended December 31, 2009, compared to a net loss attributable to OneBeacon's common shareholders of $382.7 million in the year ended December 31, 2008.
Our income tax expense (benefit) related to pre-tax income (loss) for the years ended December 31, 2009 and 2008 represented effective tax rates of 24.7% and (36.6)%, respectively. The effective tax rate for the year ended December 31, 2009 was lower than the U.S. statutory rate of 35% primarily due to income generated in jurisdictions other than the United States and the settlement of federal income tax audits for 2003 and 2004. Our effective tax rate for the year ended December 31, 2008 was higher than the U.S. statutory rate of 35% due to a pre-tax loss from operations in the United States and income generated in jurisdictions other than the United States, partially offset by non-deductible dividends and accretion on the Berkshire Preferred Stock.
Cash flows from investing and financing activities for the year ended December 31, 2008
During 2008, we declared and paid $80.2 million of regular quarterly cash dividends and $195.3 million of a special dividend to holders of OneBeacon's common shares.
At December 31, 2010 and 2009, we held one private preferred stock that represented approximately 86% and 98%, respectively, of our preferred stock portfolio. We used quoted market prices for similar securities that were adjusted to reflect management's best estimate of fair value; this security is classified as a Level 3 measurement.
Immediately preceding the OneBeacon Acquisition, we purchased a reinsurance contract with NICO under which we are entitled to recover from NICO up to $2.5 billion in the future for asbestos claims arising from business written by us in 1992 and prior, environmental claims arising from business written by us in 1987 and prior, and certain other exposures. Under the terms of the NICO Cover, NICO receives the economic benefit of reinsurance recoverables from certain of our third-party reinsurers in existence at the time the NICO Cover was executed, or Third-Party Recoverables. As a result, the Third-Party Recoverables serve to protect the $2.5 billion limit of NICO coverage for the benefit of us. Any amounts uncollectible from third-party reinsurers due to dispute or the reinsurers' financial inability to pay are covered by NICO under its agreement with us. Third-Party Recoverables are typically for the amount of loss in excess of a stated level each year. Of claim payments from 2000 through 2010, approximately 44% of A&E losses have been recovered under the historical third-party reinsurance.
At December 31, 2008, management had estimated that future payments from personal injury protection (PIP) litigation from our AutoOne business would be approximately $7.8 million. During 2009, the legal expenses related to this litigation were higher than expected. As a result, management increased estimates of all accident years for AutoOne. The total increase in estimate was $33.3 million which affected Other Insurance Operations.