assessments. Because litigation and other contingencies are inherently unpredictable and excessive verdicts do occur, these assessments can involve a series of complex judgments about future events and can rely heavily on estimates and assumptions.

Acquisitions

Our consolidated financial statements include an acquired business’s operations after the completion of the acquisition. We account for acquired businesses using the acquisition method of accounting. The acquisition method of accounting for acquired businesses requires, among other things, that most assets acquired and liabilities assumed be recognized at their fair values as of the acquisition date and that the fair value of acquired in-process research and development (IPR&D) be recorded on the balance sheet. Also, transaction costs are expensed as incurred. Any excess of the purchase price over the assigned values of the net assets acquired is recorded as goodwill. For acquisitions consummated prior to January 1, 2009, amounts allocated to acquired IPR&D were expensed at the date of acquisition. When we have acquired net assets that do not constitute a business under U.S. GAAP, no goodwill has been recognized.

Contingent consideration is included within the acquisition cost and is recognized at its fair value on acquisition date. A liability resulting from contingent consideration is remeasured to fair value at each reporting date until the contingency is resolved. Changes in fair value are recognized in earnings.

Fair Value

We often are required to measure certain assets and liabilities at fair value, either upon initial measurement or for subsequent accounting or reporting. For example, we use fair value extensively in the initial measurement of net assets acquired in a business combination and when accounting for and reporting on certain financial instruments. We estimate fair value using an exit price approach, which requires, among other things, that we determine the price that would be received to sell an asset or paid to transfer a liability in an orderly market. The determination of an exit price is considered from the perspective of market participants, considering the highest and best use of assets and, for liabilities, assuming the risk of non-performance will be the same before and after the transfer. Many, but not all, of our financial instruments are carried at fair value. In addition, as required under accounting rules for business combinations, most of the assets acquired and liabilities assumed from Wyeth on October 15, 2009 have been recorded at their estimated fair values as of the acquisition date (see the “Acquisition of Wyeth” section of this Financial Review for additional information). For additional information on the valuation approaches allowed under U.S. GAAP to determine fair value, including a description of the inputs used, see Notes to Consolidated Financial Statements––Note 1F. Significant Accounting Polices: Fair Value. Also, for information on the use of fair value for our financial instruments, see Notes to Consolidated Financial Statements—Note 9. Financial Instruments.

Revenues

Revenue Recognition—We record revenues from product sales