# The Probability of Winning and the Effect of Home-Field Advantage: The Case of Major League Baseball

## Article excerpt

ABSTRACT

This paper examines the factors that affect the probability of a major league baseball team winning a game. The basic hypotheses of the study are that home teams are more likely to win a game than visiting teams, that teams that travel to arrive at a game are less likely to win the game than teams that don't, and that teams having a strong batting performance are more likely to win a game than teams having a weak batting performance. To examine these issues, we estimate five logit regressions from data for all 2,428 regular season games played during the 2004 season. We find that while the strength of a team's batting performance does affect its probability of winning, travel does not affect the likelihood of either the home team or visiting team winning a game. The major finding of the paper, however, is that contrary to the commonly held belief that a home-field advantage exists in major league baseball games, home teams only have an advantage over visiting teams in very close games. In games that are won by more than one run, the likelihood of winning is roughly equal for home teams and visiting teams.

INTRODUCTION

In major league baseball, like most other professional sports, the conventional wisdom is that a home-field advantage exists. Birnbaum (2004, p. 972) reports that home teams have historically won about 54 percent of their games. The difference between a 54 percent winning percentage and a 46 percent winning percentage is substantial since, during a standard 162-game season, a team that wins 54 percent of its games will accumulate 12 more victories than a team that wins 46 percent of its games. Twelve additional wins during the course of a season often makes the difference between a team going to the post-season playoffs and not going to the playoffs. In the two most recent seasons, 2003 and 2004, the first place team won fewer than twelve more games than the second place team in five of the six Major League Baseball divisions.1

One reason the home team has the advantage in baseball is the fact that they bat last, which becomes a factor in one-run victories. If a game enters the top of the last inning with the score tied, for example, the manager of the visiting team doesn't know whether his strategy should involve trying to score a single run, since he doesn't know whether or not one run will ultimately be enough to win the game. If the score is tied entering the bottom of the last inning, however, the manager of the home team knows that a single run will be enough to win the game, and he can therefore employ a strategy designed to score just one run. Another possible reason that a ho me team has an advantage is that the visiting team experiences travel-induced stress and fatigue. Since the visiting team must travel to arrive at a game, it incurs the inconveniences associated with travel, in terms of both the physical act of traveling and the act of staying in an unfamiliar city. In some cases the home team also incurs the inconvenience of travel.2 If the home team does travel, they would be subjected to the same travel-induced fatigue as the visiting team, but they would not experience the discomfort of being away from the familiar surroundings of home. As such, when both teams travel to a game the visiting team is more likely than the home team to be adversely affected by the travel.

The primary purpose of this paper is to determine the effect that ho me-field advantage has on the probability of a team winning a major league baseball game played during the 2004 season. We also determine the effect that team batting performance and travel have on the probability of a team winning a game. Specifically, we will determine whether a home-field advantage exists and, if so, whether it exists generally or only in limited situations. To examine these issues we develop and estimate a series of binary logit regressions where the outcome of the game (i.e., win or lose) is the dependent variable. …