Following Krautmann and Donley (2009), we use data on the gross marginal revenue products (MRP) of baseball players as calculated by Bradbury (2007, Appendix D). Bradbury assigns these values to each player by following a modified approach to the methodology used in Scully (1974). First, he creates a production function that estimates a team’s run differential (RD) defined as the difference between runs scored (RS) and runs allowed (RA). Then he uses the player’s realized performance to compute the player’s contribution to RD. Bradbury uses a quadratic revenue function to convert RD into team revenues (TR), and finally Bradbury is able to use these results to record a MRP value for each player where MRP is a function of that player’s realized performance.The dependent variable, SHIRK, is the wage of each player minus his MRP: