Monte-Carlo Simulation of J1 League Postseason System from the 2015 Season

TL;DR

This study uses Monte-Carlo simulation to analyze the 2015 J1 League postseason system, revealing overlaps and probabilities of different postseason sizes, and concludes the system functions more like a one-stage format.

Contribution

The paper provides a quantitative assessment of the new postseason system's structure and effectiveness through simulation, highlighting its overlap issues and actual operational format.

Findings

Average of 3.5 teams reach postseason

Probability of 3, 4, and 5 teams in postseason are 0.62, 0.35, and 0.03

The system functions mainly as a one-stage system

Abstract

In this paper, the new two stage and postseason system of J1 League, the top division of professional football in Japan, is simulated. Official regulation defines that the new postseason from the 2015 season consists of five teams selected by different principles --- the top three teams by total season points, and the winning teams of the 1st and 2nd half of the season. This paper clarifies that there are overlaps within these five teams and the average number of teams reaching the postseason is about 3.5. The probability that the postseason is held with 3, 4, and 5 teams are estimated about 0.62, 0.35, and 0.03, respectively. From this result, this paper concludes that the new system of J1 League is basically a one-stage system, whereas the new system is officially defined as a two-stage system, due to inappropriate design of the postseason.