This excerpt taken from the AAPL DEF 14A filed Jan 7, 2009.
2. Criteria for Performance-Based Cash Incentives
In fiscal 2009, the Compensation Committee determined that it was appropriate to change the performance criteria used in determining the Companys performance-based cash incentives from revenue and operating income to adjusted sales and adjusted operating income. The Company has disclosed certain adjusted non-GAAP financial measures to provide insight into operating and business trends not readily apparent from GAAP results, as described in its report on Form 8-K filed with the SEC on October 21, 2008. The Compensation Committee believes it is important to align the named executive officers performance-based cash payments with these measures, as these are the measures that the Companys management uses in analyzing the business.