The Relationship Between MLB ® Team Records and the World Series ®

With the MLB playoffs and World Series approaching, I thought it might be interesting to look at a MLB team's regular season record and determine if a correlation exists between a team's winning percentage and how far they advance in the playoffs. Compared to other professional sports leagues, the MLB playoffs are very restrictive in terms of team entry. Only 8 MLB teams out of 30 (26.67%) are eligible for the MLB playoffs. Compare this percentage to the playoffs for the NFL (37.5%), NBA and NHL (53.3% each). But as the MLB regular season is long and spans 162 games, it is possible a correlation exists between a team's winning percentage and how far a MLB team tends to go in the playoffs. Therefore, this article examines the regular season winning percentages of teams eligible for the MLB playoffs from 1995 to 2009 and takes a quick look at how well these MLB teams advanced into the playoffs, broken down into the American and National Leagues.

Using winning percentages as an average, with the American League there is a slight correlation regarding a MLB team's regular season winning percentage and how far they advance into the MLB playoffs. Starting with the American League, the average winning percentage of American League teams entering the Divisional Series from 1995 through 2009 is 0.590 (standard deviation = 0.037). The average winning percentage of teams reaching the League Championship Series is 0.598 (standard deviation = 0.044). American League teams reaching the World Series have an average winning percentage of 0.606 (standard deviation = 0.044). And finally, American League teams winning the World Series have an average winning percentage of 0.608 (standard deviation = 0.045).

Looking at the National League, teams entering the playoffs have an average regular season winning percentage of 0.576 (standard deviation = 0.035). National League teams reaching the League Championship Series and the World Series both have an average winning percentage of 0.582 (standard deviation = 0.035). Interestingly, National League teams that have won the World Series have a low average winning percentage of 0.567 (standard deviation = 0.034). This is perhaps in part to the St. Louis Cardinals World Series victory in 2006 as the Cardinals team that year entered the playoffs with a regular season winning percentage of 0.516.

Therefore, with the American League, there is a slight correlation with a higher winning percentage and advancement in the MLB playoffs. In the National League, the correlation exists as teams move from the Divisional Series to the League Championship Series and World Series but the average difference is less when compared to the American League. And interestingly, National League teams who have won the World Series have on average a lower winning percentage. I hope you have found this short article to be interesting and informative. And please visit some of my other articles on playoff statistics such as the one I've wrote for AFC and NFC teams in the NFL.