Playing with models.

It’s true: Cubs choke while Yankees surge.

Posted in Sports, Statistics by Alexander Lobkovsky Meitiv on March 24, 2010

1969 Chicago Cubs Photo with autographs

The infamous chokers: 1969 Chicago Cubs

The fans of Chicago Cubs know this scenario all too well. The Cubs, a great team, have a decent season only to slump and choke at the end. You only have to google the words “Cubs choke” to come up with dozens of websites lamenting the numerous heartbreaks. Cubs fans have developed a kind of fatalistic gloom as a coping strategy.

Then there are the Yankees everyone loves to hate. They seem to elevate their game at the end of the season and transform from a good team to hall of fame greatness. It’s as if all season long they weren’t giving it all they got during the regular season. It seems that they play just well enough to get into the postseason only to turn on the afterburners and blow everyone away.

Are these notions fiction perpetrated by fans or fact based on evidence?

We are in a position to test these hypothesis using a scientifically sound ELO ranking system. Using publicly available match data I compiled ELO ratings for all baseball teams going back to 1874. To refresh your memory, an ELO rating is a number which measures the true strength of a team based on all previous games. It is supposed to track the current strength accurately and in an unbiased manner.

The ratings of the 1977 Yankees and the 1969 Cubs

Variation of the ELO rating of the Cubs and Yankees during the 1969 and 1977 seasons.


The graph of the infamous 1969 Cubs choke and the Yankees 1977 season in which they won the World Series after being 51-44 in July and ranked #3 seems to support the “Cubs choke Yankees surge” hypothesis.

Is this true in general or is it just a lucky or unlucky break?

Well, here is where the data analysis can fully demonstrate its magic. The numbers don’t lie. If whoever does the numbers doesn’t that is.

What I did is to compute the difference between the rating of each team at the end of the season and its rating on September 1st of the same season. I then averaged this late season rating change over the last 47 years (since the 1961 expansion of the leagues from 16 to 20 teams). I then tested the result against the hypothesis that the rating change is purely random. This test weeded out the teams whose late season rating change could have resulted from purely random rating fluctuations. The remaining teams’ late season change is statistically significant and therefore not a fluke.

The result clearly supports the “Cubs choke, Yankees surge hypothesis.”

Bargraph of the average late season rating change.

The average late season rating change for 9 teams whose rating change is statistically significant.

Legend:
ANA: Angels
CHW: White Sox
OAK: Athletics
STL: Cardinals
ATL: Braves
TEX: Rangers
CHC: Cubs
NYY: Yankees
DET: Tigers