Much is made ado about how the American League East (ALE) is a very difficult division to play in. Pitchers that put up lines that are similar to their non-
elite East brethren are considered better for braving the wilds of a division filled with evil genius GMs, boatloads of bucks, and enough name-cache to make Ken Rosenthal sport wood. I’ve always wondered just how large this effect is and if there is a way to normalize players lines within the division so that we can get a better idea of how they compare to their peers. The chart below shows how each division fared against the other three and overall. For instance, in the first section we can see the typical line put up by the American League Central (ALC) versus the ALE, American League West (ALW), and the overall total. As a further example, you would say that the ALC batters put up a triple slash of .262/.332/.425 versus the ALE, good for a wOBA of .339. You can look at these for each division versus each division, but what I want to focus on is the Total chart that can be found at the bottom.
I like this portion of the chart because it gives a great idea about how the entirety of the American League played against the ALE in 2010. The average American Leaguer had a .330 wOBA while posting a triple slash of .259/.326/.406 while walking 8.5% of the time and striking out 17.7% of the time. This mythical “average” player popped a dinger about 2.6% of his plate appearances while hitting for extra bases around 7.7% of his trips to the dish. Once on, this player had a stolen base success rate of around 73.7%. The average American League batter scored around .12 runs per plate appearance and if you extrapolate that out to the average number of plate appearances per game in 2010 (38) this player scored around 4.42 runs per game.
We can compare how this player performed against teams from the ALE by dividing each category by the grand total. Doing this for all categories yields a chart like the one below:
You would read this as, “The average American League player saw a 2.2% increase to his wOBA when playing a team from the American League East.” You can do this across all categories, eventually getting to the point that you would expect the average team to score 6.4% more runs than usual when playing a team from the ALE. It sure seems to me that when playing these beastly teams you can expect to see your favorite team’s offense perform a bit better than the norm, which makes me wonder just how strong the pitching and defense actually is in the ALE.
Click HERE if you would like to download the workbook. It may help give a better understanding of my methodology and it includes t-tests and other relevant statistics comparing each of the independent variables to R/PA, the dependent variable. Thanks for taking the time.