Market risk is the risk of the loss of fair value resulting from adverse changes in market rates and prices, such as interest rates and foreign currency exchange rates. Market risk is directly influenced by the volatility and liquidity in the markets in which the related underlying financial instruments are traded. Sensitivity analysis measures the impact of hypothetical changes in interest rates, foreign exchange rates and other market rates or prices on the profitability of market-sensitive financial instruments.
The following discussion about the potential effects of changes in interest rates and Canadian currency exchange rates is based on shock-tests, which model the effects of interest rate and Canadian exchange rate shifts on our financial condition and results of operations. Although we believe shock tests provide the most meaningful analysis permitted by the rules and regulations of the SEC, they are constrained by several factors, including the necessity to conduct the analysis based on a single point in time and by their inability to include the extraordinarily complex market reactions that normally would arise from the market shifts modeled. Although the following results of shock tests for changes in interest rates and Canadian currency exchange rates may have some limited use as benchmarks, they should not be viewed as forecasts. These disclosures also are selective in nature and address, in the case of interest rates, only the potential direct impact on our financial instruments, and in the case of Canadian currency exchange rates, the potential translation impact on net income from our Canadian subsidiaries. They do not include a variety of other potential factors that could affect our business as a result of these changes in interest rates and Canadian currency exchange rates.
Interest Rate Risk
The fair value of the fixed-maturity securities in our invested asset portfolio as of December 31, 2011 was $1.97 billion. The primary market risk for this portion of our invested asset portfolio is interest rate risk. One means of assessing the exposure of our fixed-maturity securities portfolios to interest rate changes is a duration-based analysis that measures the potential changes in market value resulting from a hypothetical change in interest rates of 100 basis points across all maturities. This model is sometimes referred to as a parallel shift in the yield curve. Under this model, with all other factors constant and assuming no offsetting change in the value of our liabilities, we estimated that such an increase in interest rates would cause the market value of our fixed-maturity securities portfolios to decline by approximately $61.6 million, or 3%, based on our actual securities positions as of December 31, 2011.
Canadian Currency Risk
We also have exposure to foreign currency exchange risk to the extent we conduct business in Canada. For the year ended December 31, 2011, 19% of our revenues from operations, excluding realized investment gains, were generated by our Canadian operations. A strong Canadian dollar relative to the U.S. dollar results in higher levels of reported revenues, expenses, net income, assets, liabilities and accumulated other comprehensive income (loss) in our U.S. dollar financial statements and a weaker Canadian dollar has the opposite effect. Historically, we have not hedged this exposure, although we may elect to do so in future periods.
One means of assessing exposure to changes in Canadian currency exchange rates is to model the effects on reported income using a sensitivity analysis. We analyzed our Canadian currency exposure for the year ended December 31, 2011. Net exposure was measured assuming a 10% decrease in Canadian currency exchange rates compared to the U.S. dollar. We estimated that such a decrease would decrease our net income before income taxes for the year ended December 31, 2011 by approximately $6.3 million.

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