calculation of similar measures of other companies. Adjusted income is presented solely to permit investors to more fully understand how management assesses performance.

We also recognize that, as an internal measure of performance, the Adjusted income measure has limitations, and we do not restrict our performance-management process solely to this metric. A limitation of the Adjusted income measure is that it provides a view of our operations without including all events during a period, such as the effects of an acquisition or amortization of purchased intangibles, and does not provide a comparable view of our performance to other companies in the biopharmaceutical industry. We also use other specifically tailored tools designed to achieve the highest levels of performance. For example, our R&D organization has productivity targets, upon which its effectiveness is measured. In addition, the earn-out of Performance Share Award grants is determined based on a formula that measures our performance using relative total shareholder return.

Purchase Accounting Adjustments

Adjusted income is calculated prior to considering certain significant purchase accounting impacts resulting from business combinations and net asset acquisitions. These impacts, primarily associated with Pharmacia (acquired in 2003), Wyeth (acquired in 2009) and King (acquired in 2011), can include the incremental charge to cost of sales from the sale of acquired inventory that was written up to fair value, amortization related to the increase in fair value of the acquired finite-lived intangible assets, depreciation related to the increase/decrease in fair value of the acquired fixed assets, amortization related to the increase in fair value of acquired debt, and the fair value changes associated with contingent consideration. Therefore, the Adjusted income measure includes the revenues earned upon the sale of the acquired products without considering the acquisition cost of those products.

Certain of the purchase accounting adjustments can occur through 20 or more years, but this presentation provides an alternative view of our performance that is used by management to internally assess business performance. We believe the elimination of amortization attributable to acquired intangible assets provides management and investors an alternative view of our business results by trying to provide a degree of parity to internally developed intangible assets for which research and development costs previously have been expensed.

However, a completely accurate comparison of internally developed intangible assets and acquired intangible assets cannot be achieved through Adjusted income. This component of Adjusted income is derived solely from the impacts of the items listed in the first paragraph of this section. We have not factored in the impacts of any other differences in experience that might have occurred if we had discovered and developed those intangible assets on our own, and this approach does not intend to be representative of the results that would have occurred in those circumstances. For example, our research and development costs in total, and in the periods