Zimmerman: Home-field advantage in the first inning

From Jeff Zimmerman at FanGraphs on September 16, 2013, with mention of SABR member Matt Swartz:

The home team has consistently, on a year-to-year basis, won 54% of its games. Several reasons have been explored for the disparity, such as familiarity to the home field and the umpire’s biased strike zone. Another aspect that comes into play is a first-inning discrepancy in favor of the home teams’ pitchers. They have an abnormally large advantage in strikeout and walk rates, partially because of a higher fastball velocity.

Note: For consistency throughout the article, when I refer to K/BB, it will be in reference to pitchers.

With better use of bullpens and more patient hitters, strikeout and walk rates have climbed in recent years. Since 1950 (the extent of Retrosheet’s data set), the home team has always maintained a higher K/BB ratio than the away team.


While reading many articles on this subject I came across this little tidbit, from our own Matt Swartz, while he was at Baseball Prospectus:

That first-inning differential is particularly interesting, because it could be caused by another factor. Instead of the issue being that the home pitcher was more familiar with the mound than the visiting pitcher, perhaps the home pitcher is just more prone to be more effective immediately after warming up. Maybe a home pitcher knows the exact moment that he is going to step on the mound and can warm up until a couple minutes beforehand, and maybe a visiting pitcher loses focus and cools off while in the dugout waiting for his team to finish batting in the top of the first inning before getting the ball. While first warning readers about the small sample size, I can now say that we do see some clear indications that the first-inning warm-up effect may be part of home-field advantage.

Read the full article here: http://www.fangraphs.com/blogs/first-inning-home-field-advantage/

Originally published: September 16, 2013. Last Updated: September 16, 2013.