Visualizing the Home Run Efficiency Gap

As a follow-up to last week’s post on making the most of home runs

, I made two graphs to show the impact of baserunners on home run production.

The first graph starts with each team’s average number of baserunners per plate appearance (BR/PA). This includes only runners who are actually on the bases at the end of a plate appearance (I got this info from each team’s splits at baseball-reference.com

). This is different from the total number of times on base for a team, though the two numbers are obviously very highly correlated.

Anyway, the average BR/PA are represented by the gray bars. The BR/PA numbers are on the left of the graph (right next to the team name), in white. On top of those bars are green bars that represent the average number of baserunners per home runner (BR/HR). The BR/HR numbers are on the inside right end of the green bars, in black.

The difference between these two numbers can be found at the far right of each team’s bar, in green italics. Negative is bad and positive is good.

OK, sorry for all that introduction. Here’s the graph:

The teams that have benefitted the most from extra baserunners in HR situations are a mixed bag. The Yankees, Rockies, and D’backs you might expect, but the Orioles, Nationals, and Cubs? That’s interesting. I’d think that most of these gaps would regress to the mean over the course of the year. Certainly some of the teams on the lower end will get a boost. All it takes is a grand slam or two to fix those really low BR/HR numbers.

This graph is similar to the last one. The gray bar is the expected number of RBIs on home runs for each team, given the number of home runs it has hit. This is just the BR/PA number multiplied by the number of home runs. The blue bar is the actual number of RBIs the team has had on home runs. The difference is in blue italics to the right.

As a Braves fan, I’m really hoping their HR RBI differential will turn around as the year progresses. With the Braves’ pitching staff, it won’t take many more runs to make them a playoff team. On the other hand, the Yankees and especially the D’backs probably need some extra runs if they’re going to cover for their pitching staffs.