This excerpt taken from the C 10-Q filed Aug 7, 2009.
17. FAIR-VALUE MEASUREMENT (SFAS 157/ASC 820-10)
Effective January 1, 2007, the Company adopted SFAS 157(ASC 820-10). SFAS 157(ASC 820-10) defines fair value, establishes a consistent framework for measuring fair value and expands disclosure requirements about fair-value measurements. SFAS 157(ASC 820-10), among other things, requires the Company to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. In addition, SFAS 157(ASC 820-10) precludes the use of block discounts when measuring the fair value of instruments traded in an active market; such discounts were previously applied to large holdings of publicly traded equity securities. It also requires recognition of trade-date gains related to certain derivative transactions whose fair value has been determined using unobservable market inputs. This guidance supersedes the guidance in Emerging Issues Task Force 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 Issue 02-3), which prohibited the recognition of trade-date gains for such derivative transactions when determining the fair value of instruments not traded in an active market.
As a result of the adoption of SFAS 157(ASC 820-10), the Company made some amendments to the techniques used in measuring the fair value of derivative and other positions. These amendments change the way that the probability of default of a counterparty is factored into the valuation of derivative positions, include for the first time the impact of Citigroup's own credit risk on derivatives and other liabilities measured at fair value, and also eliminate the portfolio servicing adjustment that is no longer necessary under SFAS 157(ASC 820-10).