The following paragraphs define each non-GAAP financial measure and describe why it is useful. A reconciliation of the non-GAAP financial measure and the most directly comparable GAAP financial measure, if available, is presented herein. Non-GAAP financial measures should not be viewed as substitutes for their most directly comparable GAAP measures.Operating Income: Management believes that operating income is a useful measure because it clarifies the understanding of the underwriting results of the Company's financial guaranty insurance business, and also includes financing costs and net investment income, and enables investors and analysts to evaluate the Company's financial results as compared with the consensus analyst estimates distributed publicly by financial databases. Operating income is defined as net income (loss) attributable to AGL, as reported under GAAP, adjusted for the following: 1) Elimination of the after-tax realized gains (losses) on the Company's investments, except for gains and losses on securities classified as trading. The timing of realized gains and losses, which depends largely on market credit cycles, can vary considerably across periods. The timing of sales is largely subject to the Company's discretion and influenced by market opportunities, as well as the Company's tax and capital profile. Trends in the underlying profitability of the Company's business can be more clearly identified without the fluctuating effects of these transactions. 2) Elimination of the after-tax non-credit-impairment unrealized fair value gains (losses) on credit derivatives, which is the amount in excess of the present value of the expected estimated economic credit losses and non-economic payments. Such fair value adjustments are heavily affected by, and in part fluctuate with, changes in market interest rates, credit spreads and other market factors and are not expected to result in an economic gain or loss. Additionally, such adjustments present all financial guaranty contracts on a more consistent basis of accounting, whether or not they are subject to derivative accounting rules.