Undestanding Baseball Team Standings and Streaks

TL;DR

This paper uses the Bradley-Terry model to analyze baseball team standings and streaks, finding that long winning or losing streaks are mainly due to chance rather than self-reinforcing effects, and that recent decades are more competitive.

Contribution

It applies a minimalist heterogeneity model to explain baseball streaks and standings, providing statistical insights into their origins and recent competitiveness.

Findings

Good agreement between model predictions and recent streak data

Long streaks are mostly statistical, not self-reinforcing

Recent decades show increased competitiveness

Abstract

Can one understand the statistics of wins and losses of baseball teams? Are their consecutive-game winning and losing streaks self-reinforcing or can they be described statistically? We apply the Bradley-Terry model, which incorporates the heterogeneity of team strengths in a minimalist way, to answer these questions. Excellent agreement is found between the predictions of the Bradley-Terry model and the rank dependence of the average number team wins and losses in major-league baseball over the past century when the distribution of team strengths is taken to be uniformly distributed over a finite range. Using this uniform strength distribution, we also find very good agreement between model predictions and the observed distribution of consecutive-game team winning and losing streaks over the last half-century; however, the agreement is less good for the previous half-century. The behavior of the last half-century supports the hypothesis that long streaks are primarily statistical in origin with little self-reinforcing component. The data further show that the past half-century of baseball has been more competitive than the preceding half-century.