The widespread use of accounting information by investors and financial analysts to help value stocks creates an incentive for managers to manipulate earnings in an attempt to influence short-term stock price performance. This paper examines the role of earnings management in affecting a firm's cost of capital. Using an agency model with multiple firms whose cash flows are correlated, we demonstrate that the extent of earnings manipulation varies across the business cycle. Depending on a firm's earnings profile, it can have stronger incentives to overstate its performance in good times or in bad times. Because of this dependence on the state of the economy, earnings manipulation can influence a firm's cost of capital despite the forces of diversification.