Much of the theory in personnel economics relates to effects of monetary incentives on output, but the theory was untested because appropriate data were unavailable. A new data set for the Safelite Glass Corporation tests the predictions that average productivity will rise, the firm will attract a more able workforce, and variance in output across individuals at the firm will rise when it shifts to piece rates. In Safelite, productivity effects amount to a 44-percent increase in output per worker. This firm apparently had selected a suboptimal compensation system, as profits also increased with the change. (JEL J00, J22, J3)

Variable pay is usually defined as pay that is tied to some measure of worker output. The most typical form of variable pay historically was the piece rate, which was more prevalent during the early part of the 20th century than it is at the beginning of the 21st. There is a resurgence in variable pay, particularly as it relates to executives, whose pay is tied to output through some mechanism like stock options or bonuses that depend on individual or firm performance. Why use variable pay? The typical reaction is that variable pay provides incentives to put forth effort. Although true, discrete-pay schemes also generate incentives. Much of the confusion in the literature results from the use of the terms high-powered and low-powered incentives, which connote difference in ability to elicit worker effort.' It is more informative to make distinctions between discrete and continuous pay and between inputbased and output-based pay.2 Pay structures can be summarized by the following equation: