Our significant accounting principles, as described in Note 1 of the Consolidated Financial Statements, are essential in understanding Management's Discussion and Analysis of Financial Condition and Results of Operations. Many of our significant accounting principles require complex judgments to estimate values of assets and liabilities. We have procedures and processes to facilitate making these judgments.

The more judgmental estimates are summarized below. We have identified and described the development of the variables most important in the estimation process that, with the exception of accrued taxes, involve mathematical models to derive the estimates. In many cases, there are numerous alternative judgments that could be used in the process of determining the inputs to the model. Where alternatives exist, we have used the factors that we believe represent the most reasonable value in developing the inputs. Actual performance that differs from our estimates of the key variables could impact Net Income. Separate from the possible future impact to Net Income from input and model variables, the value of our lending portfolio and market sensitive assets and liabilities may change subsequent to the balance sheet measurement, often significantly, due to the nature and magnitude of future credit and market conditions. Such credit and market conditions may change quickly and in unforeseen ways and the resulting volatility could have a significant, negative effect on future operating results. These fluctuations would not be indicative of deficiencies in our models or inputs.

Allowance for Credit Losses

The allowance for credit losses is our estimate of probable losses in the loans and leases portfolio and within our unfunded lending commitments. Changes to the allowance for credit losses are reported in the Consolidated Statement of Income in the Provision for Credit Losses. Our process for determining the allowance for credit losses is discussed in the Credit Risk Management section and Note 1 of the Consolidated Financial Statements. Due to the variability in the drivers of the assumptions made in this process, estimates of the portfolio's inherent risks and overall collectibility change with changes in the economy, individual industries, countries and individual borrowers' or counterparties' ability and willingness to repay their obligations. The degree to which any particular assumption affects the allowance for credit losses depends on the severity of the change and its relationship to the other assumptions.

Key judgments used in determining the allowance for credit losses include: (i) risk ratings for pools of commercial loans and leases, (ii) market and collateral values and discount rates for individually evaluated loans, (iii) product type classifications for consumer and commercial loans and leases, (iv) loss rates used for consumer and commercial loans and leases, (v) adjustments made to assess current events and conditions, (vi) considerations regarding domestic and global economic uncertainty, and (vii) overall credit conditions.

Our Allowance for Loan and Lease Losses is sensitive to the risk rating assigned to commercial loans and leases. Assuming a downgrade of one level in the internal risk rating for commercial loans and leases rated under the internal risk rating scale, except loans and leases already risk rated Doubtful as defined by regulatory authorities, the Allowance for Loan and Lease Losses would increase by approximately $830 million at December 31, 2006. The Allowance for Loan and Lease Losses as a percentage of loan and lease outstandings at December 31, 2006 was 1.28 percent and this hypothetical increase in the allowance would raise the ratio to approximately 1.39 percent. Our Allowance for Loan and Lease Losses is also sensitive to the loss rates used for the consumer and commercial portfolios. A 10 percent increase in the loss rates used on the consumer and commercial loan and lease portfolios would increase the Allowance for Loan and Lease Losses at December 31, 2006 by approximately $610 million, of which $515 million would relate to consumer and $95 million to commercial.

These sensitivity analyses do not represent management's expectations of the deterioration in risk ratings or the increases in loss rates but are provided as hypothetical scenarios to assess the sensitivity of the Allowance for Loan and Lease Losses to changes in key inputs. We believe the risk ratings and loss severities currently in use are appropriate and that the probability of a downgrade of one level of the internal risk ratings for commercial loans and leases within a short period of time is remote.

The process of determining the level of the allowance for credit losses requires a high degree of judgment. It is possible that others, given the same information, may at any point in time reach different reasonable conclusions.

Fair Value of Financial Instruments

Trading Account Assets and Liabilities are recorded at fair value, which is primarily based on actively traded markets where prices are based on either direct market quotes or observed transactions. Liquidity is a significant factor in the determination of the fair value of Trading Account Assets or Liabilities. Market price quotes may not be readily available for some positions, or positions within a market sector where trading activity has slowed significantly or ceased. Situations of illiquidity generally are triggered by the market's perception of credit uncertainty regarding a single company or a specific market sector. In these instances, fair value is determined based on limited available market information and other factors, principally from reviewing the issuer's financial statements and changes in credit ratings made by one or more rating agencies. At December 31, 2006, $8.4 billion, or six percent, of Trading Account Assets were fair valued using these alternative approaches. An immaterial amount of Trading Account Liabilities were fair valued using these alternative approaches at December 31, 2006.

The fair values of Derivative Assets and Liabilities include adjustments for market liquidity, counterparty credit quality, future servicing costs and other deal specific factors, where appropriate. To ensure the prudent application of estimates and management judgment in determining the fair value of Derivative Assets and Liabilities, various processes and controls have been adopted, which include: a Model Validation Policy that requires a review and approval of quantitative models used for deal pricing, financial statement fair value determination and risk quantification; a Trading Product Valuation Policy that requires verification of all traded product valuations; and a periodic review and substantiation of daily profit and loss reporting for all traded products. These processes and controls are performed independently of the business segments.

The fair values of Derivative Assets and Liabilities traded in the over-the-counter market are determined using quantitative models that require the use of multiple market inputs including interest rates, prices, and indices to generate continuous yield or pricing curves and volatility factors, which are used to value the position. The predominance of market inputs are actively quoted and can be validated through external sources, including brokers, market transactions and third-party pricing services. Estimation risk is greater for derivative asset and liability positions that are either option-based or have longer maturity dates where observable market inputs are less readily available or are unobservable, in which case quantitative based extrapolations of rate, price or index scenarios are used in determining fair values. At December 31, 2006, the fair values of Derivative Assets and Liabilities determined by these quantitative models were $29.0 billion and $27.7 billion. These amounts reflect the full fair value of the derivatives and do not isolate the discrete value associated with the subjective valuation variable. Further, they represent 12.3 percent and 12.2 percent of Derivative Assets and Liabilities, before the impact of legally enforceable master netting agreements. For the year ended December 31, 2006, there were no changes to the quantitative models, or uses of such models, that resulted in a material adjustment to the Consolidated Statement of Income.

Trading Account Profits, which represent the net amount earned from our trading positions, can be volatile and are largely driven by general market conditions and customer demand. Trading Account Profits are dependent on the volume and type of transactions, the level of risk assumed, and the volatility of price and rate movements at any given time within the ever-changing market environment. To evaluate risk in our trading activities, we focus on the actual and potential volatility of individual positions as well as portfolios. At a portfolio and corporate level, we use trading limits, stress testing and tools such as VAR modeling, which estimates a potential daily loss which is not expected to be exceeded with a specified confidence level, to measure and manage market risk. At December 31, 2006, the amount of our VAR was $48 million based on a 99 percent confidence level. For more information on VAR, see Trading Risk Management.

The Corporation recognizes gains and losses at inception of a derivative contract only if the fair value of the contract is evidenced by a quoted market price in an active market, an observable price or other market transaction, or other observable data supporting a valuation model in accordance with Emerging Issues Task Force (EITF) Issue No. 02-3, "Issues Involved in Accounting for Derivative Contracts Held for Trading Purposes and Contracts Involved in Energy Trading and Risk Management Activities" (EITF 02-3). For those gains and losses not evidenced by the above mentioned market data, the transaction price is used as the fair value of the derivative contract. Any difference between the transaction price and the model fair value is considered an unrecognized gain or loss at inception of the contract. These unrecognized gains and losses are recorded in income using the straight line method of amortization over the contractual life of the derivative contract. Earlier recognition of the full unrecognized gain or loss is permitted if the trade is terminated early, subsequent market activity is observed which supports the model fair value of the contract, or significant inputs used in the valuation model become observable in the market. As of December 31, 2006, the balance of the above unrecognized gains and losses was not material. SFAS No. 157, "Fair Value Measurements" which defines fair value, establishes a framework for measuring fair value under GAAP and enhances disclosures about fair value measurements, will nullify certain guidance in EITF 02-3 when adopted and as a result, a portion of the above unrecognized gains and losses will be accounted for as a cumulative-effect adjustment to the opening balance of Retained Earnings.

AFS Securities are recorded at fair value, which is generally based on direct market quotes from actively traded markets.

Principal Investing

Principal Investing is included within Equity Investments included in All Other. Principal Investing is comprised of a diversified portfolio of investments in privately-held and publicly-traded companies at all stages of their life cycle, from start-up to buyout. These investments are made either directly in a company or held through a fund. Some of these companies may need access to additional cash to support their long-term business models. Market conditions and company performance may impact whether funding is available from private investors or the capital markets.

Investments with active market quotes are carried at estimated fair value; however, the majority of our investments do not have publicly available price quotations. At December 31, 2006, we had nonpublic investments of $5.1 billion, or approximately 95 percent of the total portfolio. Valuation of these investments requires significant management judgment. Management determines values of the underlying investments based on multiple methodologies including in-depth semi-annual reviews of the investee's financial statements and financial condition, discounted cash flows, the prospects of the investee's industry and current overall market conditions for similar investments. In addition, on a quarterly basis as events occur or information comes to the attention of management that indicates a change in the value of an investment is warranted, investments are adjusted from their original invested amount to estimated fair values at the balance sheet date with changes being recorded in Equity Investment Gains in the Consolidated Statement of Income. Investments are not adjusted above the original amount invested unless there is clear evidence of a fair value in excess of the original invested amount. As part of the valuation process, senior management reviews the portfolio and determines when an impairment needs to be recorded. The Principal Investing portfolio is not material to our Consolidated Balance Sheet, but the impact of the valuation adjustments may be material to our operating results for any particular quarter.

Accrued Income Taxes

As more fully described in Notes 1 and 18 of the Consolidated Financial Statements, we account for income taxes in accordance with SFAS No. 109, "Accounting for Income Taxes" (SFAS 109). Accrued income taxes, reported as a component of Accrued Expenses and Other Liabilities on our Consolidated Balance Sheet, represents the net amount of current income taxes we expect to pay to or receive from various taxing jurisdictions attributable to our operations to date. We currently file income tax returns in more than 100 jurisdictions and consider many factors—including statutory, judicial and regulatory guidance—in estimating the appropriate accrued income taxes for each jurisdiction.

In applying the principles of SFAS 109, we monitor relevant tax authorities and change our estimate of accrued income taxes due to changes in income tax laws and their interpretation by the courts and regulatory authorities. These revisions of our estimate of accrued income taxes, which also may result from our own income tax planning and from the resolution of income tax controversies, may be material to our operating results for any given quarter.

Goodwill and Intangibles Assets

The nature of and accounting for Goodwill and Intangible Assets is discussed in detail in Notes 1 and 10 of the Consolidated Financial Statements. Goodwill is reviewed for potential impairment at the reporting unit level on an annual basis, or in interim periods if events or circumstances indicate a potential impairment. The reporting units utilized for this test were those that are one level below the business segments identified in Business Segment Operations. The impairment test is performed in two steps. The first step of the Goodwill impairment test compares the fair value of the reporting unit with its carrying amount, including Goodwill. If the fair value of the reporting unit exceeds its carrying amount, Goodwill of the reporting unit is considered not impaired; however, if the carrying amount of the reporting unit exceeds its fair value, the second step must be performed. The second step compares the implied fair value of the reporting unit's Goodwill, as defined in SFAS No. 142, "Goodwill and Other Intangible Assets", with the carrying amount of that Goodwill. An impairment loss is recorded to the extent that the carrying amount of Goodwill exceeds its implied fair value.

For Intangible Assets subject to amortization, impairment exists when the carrying amount of the Intangible Asset exceeds its fair value. An impairment loss will be recognized only if the carrying amount of the Intangible Asset is not recoverable and exceeds its fair value. The carrying amount of the Intangible Asset is not recoverable if it exceeds the sum of the undiscounted cash flows expected to result from it. An Intangible Asset subject to amortization shall be tested for recoverability whenever events or changes in circumstances, such as a significant or adverse change in the business climate that could affect the value of the Intangible Asset, indicate that its carrying amount may not be recoverable. An impairment loss is recorded to the extent the carrying amount of the Intangible Asset exceeds its fair value.

The fair values of the reporting units were determined using a combination of valuation techniques consistent with the income approach and the market approach and the fair values of the Intangible Assets were determined using the income approach. For purposes of the income approach, discounted cash flows were calculated by taking the net present value of estimated cash flows using a combination of historical results, estimated future cash flows and an appropriate price to earnings multiple. We use our internal forecasts to estimate future cash flows and actual results may differ from forecasted results. However, these differences have not been material and we believe that this methodology provides a reasonable means to determine fair values. Cash flows were discounted using a discount rate based on expected equity return rates, which was 11 percent for 2006. Expected rates of equity returns were estimated based on historical market returns and risk/return rates for similar industries of the reporting unit. For purposes of the market approach, valuations of reporting units were based on actual comparable market transactions and market earnings multiples for similar industries of the reporting unit.

Our evaluations for the year ended December 31, 2006 indicated there was no impairment of Goodwill or Intangible Assets.