Does a big division lead correlate to a World Series berth?

On June 15, the Minnesota Twins were 11 games ahead of the Cleveland Indians in the AL Central. At the moment of this writing, that lead has shrunk to 4 games. As expected, this has caused a wee bit of consternation around these parts, what with sky-is-falling proclamations and general negativity even causing the ban-hammer to come out from admins. Dogs and cats living together, mass hysteria, etc.

What the shrinking cushion in the AL Central got me pondering is whether the size of a division championship margin is at all predictive of playoff success. I decided to run some numbers on this issue, and here is what I discovered…

The Setup

I used 1998 as my starting point, as it provided a decent sample size and constituted the basic assemblage of teams that still comprise MLB. I defined “comfortable division victory” as anything above a four-game margin. Somewhat arbitrary, for sure, but instinctively a 5+ game division lead seemed secure in a way that 4 or less games did.

The Results

Since ’98, there have been 42 league champions (21 NL, 21 AL) out of a pool of 182 total playoff teams (division winners and wild cards). Of those 182 squads…

-76 (42%) won their division by 5+ games

-50 (27%) won their division by 4 or fewer games

-56 (32%) qualified for the playoffs as a wild card team

Narrowing down the data even further…

-Of the 76 comfortable division-winning teams, 20 secured a World Series berth.

-Of the 50 nail-biter division winners, 11 went on to compete in the Fall Classic.

-Of the 50 wild card entrees, 11 rose from that lowest slot to reach the World Series.

Ultimately, the data point I was trying to tease out ended up illustrating this:

-Teams with large (5+ games) division victories since 1998 made the World Series 48% of the time.

-Teams with small (4 or less games) division victories since 1998 made the World Series 26% of the time.

-Teams entering the playoffs on a wild card berth since 1998 made the World Series 26% of the time.

Discussion

So, does the size of a division victory have any bearing on postseason success? I would say that it does, although not mind-blowingly so. Basically, teams that handily won a division for the past 20 years had a coin-flip’s chance of reaching the Big Dance. Teams that snuck in or were a wild card had a ¼ chance. Even adding the slim division winners and wild cards together produced just a 52% chance at a WS berth despite the number of overall teams in that mix being 106 (compared to 76 at 5+ GA). Essentially, the odds of reaching the World Series as a comfortable division winner were about the same as any other path despite being a smaller cohort group. While I am not sure what classifies as “statistically significant” (I never took Stats in college), there is indeed a correlation between winning a division by 5+ games and a better chance of making the World Series.

Of course, I also realize the implicit imbalance of this study. Prior to 2012, the only real playoff disadvantage a wild card team had was starting every series on the road. Those wild card teams, in some cases, may have had better records than the division-winners, or won their own races by significant margins. I did not factor those components into my analysis.

Overall, though, I feel like Twins fans have cause to feel a little antsy. A team will never turn down a playoff slot of any kind (you have to “get in it to win it”), but there does seem to be an indication that division-winning strength may correlate with postseason glory. As such, here’s to hoping the AL Central margin starts ticking the other direction (the good one…up!) again soon.