What is the most competitive sport?

TL;DR

This paper analyzes sports competitiveness by examining team parity and game predictability across major leagues, introducing a model linking upset frequency with competitiveness and proposing upset likelihood as a key measure.

Contribution

It provides a statistical framework connecting team parity, game unpredictability, and introduces a model to estimate upset frequency from standings data.

Findings

Higher parity correlates with increased unpredictability.

The mathematical model accurately estimates upset probabilities.

Likelihood of upsets serves as a quantitative measure of competitiveness.

Abstract

We present an extensive statistical analysis of the results of all sports competitions in five major sports leagues in England and the United States. We characterize the parity among teams by the variance in the winning fraction from season-end standings data and quantify the predictability of games by the frequency of upsets from game results data. We introduce a mathematical model in which the underdog team wins with a fixed upset probability. This model quantitatively relates the parity among teams with the predictability of the games, and it can be used to estimate the upset frequency from standings data. We propose the likelihood of upsets as a measure of competitiveness.