Beyond Moneyball

This study provides an updated test of Billy Beane’s Moneyball hypothesis using a panel model over the years 1999-2013. We regressed winning percentage as a function of the original Moneyball variables, which included on-base percentage, slugging percentage, on-base percentage against and slugging percentage against. In turn we created our own model which replaced the “against” statistics with earned run average and fielding percentage. Within both models, we concluded that the coefficient of on-base percentage was significantly greater than slugging percentage, which supports Beane’s theory that in today’s game on-base percentage is more important than slugging in determining winning percentage. We extend this analysis using both models to test for the effects of the 2005 steroid ban and found that neither of the coefficients for on-base percentage or slugging percentage were significantly affected by the ban. These conclusions can be used by major league managers and owners to decide which players to trade for or to pick up in free agency