Fair Value

In the current market environment, the assessment of the fair value of debt instruments can be difficult and subjective. The volume of trading activity of certain debt instruments has declined, and the rapid changes occurring in today's financial markets can lead to changes in the fair value of financial instruments in relatively short periods of time. SFAS No. 157 establishes three levels of inputs that may be used to measure fair value (see "Note 3: Fair Value" in Part II, Item 8 of this Form 10-K). Each level of input has different levels of subjectivity and difficulty involved in determining fair value.

Level 1 instruments represent quoted prices in active markets. Therefore, determining fair value for Level 1 instruments does not require significant management judgment, and the estimation is not difficult.

Level 2 instruments include observable inputs other than Level 1 prices, such as quoted prices for identical instruments in markets with insufficient volume or infrequent transactions (less active markets), issuer credit ratings, non-binding market consensus prices that can be corroborated with observable market data, model-derived valuations in which all significant inputs are observable or can be derived principally from or corroborated with observable market data for substantially the full term of the assets or liabilities, or quoted prices for similar assets or liabilities. These Level 2 instruments require more management judgment and subjectivity compared to Level 1 instruments, including:

• Determining which instruments are most similar to the instrument being priced requires management to identify a sample of similar securities based on the coupon rates, maturity, issuer, credit rating, and instrument type, and subjectively select an individual security or multiple securities that are deemed most similar to the security being priced.
• Determining whether a market is considered active requires management judgment. Our assessment of an active market for our marketable debt instruments generally takes into consideration activity during each week of the one-month period prior to the valuation date of each individual instrument, including the number of days each individual instrument trades and the average weekly trading volume in relation to the total outstanding amount of the issued instrument.
• Determining which model-derived valuations to use in determining fair value requires management judgment. When observable market prices for identical securities or similar securities are not available, we price our marketable debt instruments using non-binding market consensus prices that are corroborated with observable market data or pricing models, such as discounted cash flow models, with all significant inputs derived from or corroborated with observable market data.

Level 3 instruments include unobservable inputs to the valuation methodology that are significant to the measurement of fair value of assets or liabilities. The determination of fair value for Level 3 instruments requires the most management judgment and subjectivity. Most of our marketable debt instruments classified as Level 3 are valued using a non-binding market consensus price or a non-binding broker quote, both of which we corroborate with unobservable data. Non-binding market consensus prices are based on the proprietary valuation models of pricing providers or brokers. These valuation models incorporate a number of inputs, including non-binding and binding broker quotes; observable market prices for identical and/or similar securities; and the internal assumptions of pricing providers or brokers that use observable market inputs, and to a lesser degree non-observable market inputs. Adjustments to the fair value of instruments priced using non-binding market consensus prices and non-binding broker quotes, and classified as Level 3, were not significant in 2008.

Other-Than-Temporary Impairment

After determining the fair value of our available-for-sale debt instruments, gains or losses on these investments are recorded to other comprehensive income, until either the investment is sold or we determine that the decline in value is other-than-temporary. Determining whether the decline in fair value is other-than-temporary requires management judgment based on the specific facts and circumstances of each investment. For investments in debt instruments, these judgments primarily consider: the financial condition and liquidity of the issuer, the issuer's credit rating, and any specific events that may cause us to believe that the debt instrument will not mature and be paid in full; and our ability and intent to hold the investment to maturity. Given the current market conditions, these judgments could prove to be wrong, and companies with relatively high credit ratings and solid financial conditions may not be able to fulfill their obligations. In addition, if management decides not to hold an investment until maturity, it may result in the recognition of an other-than-temporary impairment.

As of December 27, 2008, our investments included $11.3 billion of available-for-sale debt instruments. During 2008, we recognized $44 million in impairment charges on our available-for-sale debt instruments. As of December 27, 2008, our cumulative unrealized losses related to debt instruments classified as available-for-sale were approximately $215 million (approximately $55 million as of December 29, 2007). As of December 27, 2008, this amount included approximately $170 million of unrecognized losses that could be recognized in the future if our other-than-temporary assessment changes.