We are an exempted Bermuda limited liability company. Our operating companies are U.S.-based property and casualty insurance writers, most of which operate in a multi-company pool. Pooling arrangements permit the participating companies to rely on the capacity of the entire pool's capital and surplus rather than just on its own capital and surplus. Under such arrangements, the members share substantially all insurance business that is written, and allocate the combined premiums, losses and expenses. We provide a wide range of specialty insurance products and services through independent agencies, regional and national brokers, wholesalers and managing general agencies. In the year ended December 31, 2011, our net written premiums totaled $1.1 billion and we had total assets of approximately $5.8 billion and total OneBeacon's common shareholders' equity of $1.1 billion at December 31, 2011.
On May 25, 2011, OneBeacon issued 630,000 shares of restricted stock to its CEO that vest in equal installments on February 22, 2014, 2015, 2016 and 2017. Concurrently with the grant of the restricted stock, 35,000 performance shares issued to the CEO for the 2011-2013 performance share cycle were forfeited. Performance share awards to the CEO for the next five years will be reduced by a similar number of shares. At December 31, 2011, the Company had 630,000 unvested restricted shares outstanding.
The income tax expense related to pre-tax income from continuing operations for the years ended December 31, 2011, 2010 and 2009 represented net effective tax rates of 2.5%, 8.9% and 25.7%, respectively. Our effective tax rate for the year ended December 31, 2011 was lower than the U.S. statutory rate of 35% due to income generated in jurisdictions other than the United States, principally representing interest income taxed in a jurisdiction with a lower effective tax rate. Our 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, principally representing interest income taxed in a jurisdiction with a lower effective tax rate, and recognition of a deferred tax asset for a higher tax
our Specialty Insurance Operations combined ratio by 0.6 points, 1.7 points and 2.5 points, respectively.
Our fixed income portfolio, which includes fixed maturity and short-term investments, returned 3.4% for the year ended December 31, 2011, underperforming the Barclays U.S. Intermediate Aggregate Index returns of 6.0%. We maintained a high quality fixed maturity portfolio with a relatively short duration of approximately 2.5 years excluding short-term investments and approximately 2.2 years including short-term investments at December 31, 2011 which trailed the longer-duration benchmark as rates declined during 2011.
Ultimate loss and LAE are generally determined by extrapolation of claim emergence and settlement patterns observed in the past that can reasonably be expected to persist into the future. In forecasting ultimate loss and LAE with respect to any line of business, past experience with respect to that line of business is the primary resource, but cannot be relied upon in isolation. Our own experience, particularly claims development experience, such as trends in case reserves, payments on and closings of claims, as well as changes in business mix and coverage limits, is the most important information for estimating our reserves. External data, available from organizations such as statistical bureaus, consulting firms and reinsurance companies, is sometimes used to supplement or corroborate
The collectibility of reinsurance recoverables is subject to the solvency and willingness to pay of the reinsurer. We are selective in choosing our reinsurers, placing reinsurance principally with those reinsurers with a strong financial condition, industry ratings and underwriting ability. Management monitors the financial condition and ratings of our reinsurers on an ongoing basis. See Note 4-"Reinsurance" of the accompanying consolidated financial statements for additional information on our reinsurance programs.