It's a party in the MLB: An analysis of shirking between games in Major League Baseball

Incentives for employee exertion of effect are a concern of employers in situations where the employee feels job security. An employee is said to shirk if he or she underperforms the employer’s expectation. The Major League Baseball player market is an ideal setting to study this potential for shirking. Players frequently sign contracts that exceed one year in length, and due to the strength of the players’ union, these contracts come with pay that is guaranteed regardless of performance. Evidence from this setting suggests that player output is relatively low early in multi-year contracts and relatively high near the end of multi-year contracts.

Players have three distinct time periods in which effort levels can potentially be manipulated. The player can choose what level of effort to exert in maintaining top physical conditioning during the off-season, in remaining prepared between games during the season, and in play during games. This paper looks to identify whether one avenue through which players in the early years of multi-year contracts shirk is in the exertion of effort between games. Between games, hitters can choose how much film and information they want to consume about the next opposing pitcher. They can also choose how much sleep they get, as well as what food, drink, and other substances enter their bodies.

Daily player data are used to identify differences in player performance throughout the course of the season. Data for this study comes from dailyplayerdata.com, the Cot’s Baseball Contracts website, and the Sean Lahman database. Teams play 162 games during a 183-day regular season. Starting position players play most of these games. As teams play an average of over 6 days in a week, most games are played on consecutive days. Game start times vary from early afternoon to late evening, which means that the amount of preparation time players have between games can vary. A differences-in-differences regression strategy is used and finds that increases in contract length lead to diminished performance when a player is playing on short rest, but not when a player has longer rest. Using a triple difference estimation strategy, this study finds that this diminished performance is driven by games played on short rest in cities with the best night-life in the United States. This suggests that one avenue through which shirking occurs is diminished effort between games.