Do some teams get more favorable strike calls than others? Do the Yomiuri Giants, who have a long organizational history of writing the official rules to favor their business model, and then bending or ignoring those rules when it suits them, get the same kind of favoritism on the field?

A legion of anti-Giants fans want to believe Yomiuri catches the bulk of the breaks, and there are tons of examples where the Giants did get obviously favorable calls, but focusing on individual calls without a broader context leads to little clarity.

So I did a study of how often pitches taken are called balls, and how that differed from team to team and from batters to pitchers. Without pitch-tracking data, it’s difficult to compile objective league-wide contexts, but we do have the record of pitches that require an umpire’s judgement to call a ball or a strike.

While there will obviously be noise in such a rough sample, the study supports two conclusions: that some teams have routinely tended to get better calls than others, and that batters are responsible for the largest amount of variability in the results of plate appearances.

The data

Thanks to database wiz Michael Westbay, who has been keeping pitch data on every completed plate appearance since 2009, we can know close to how many pitches each team’s batters have taken in each year, how many were called balls and how many strikes, and how many pitches teams throw that result in called balls and strikes.

I presented some information about batters recently, and found that Seibu has received more than the Lions’ share of called balls since 2009. I am excluding the 2020 season because Westbay’s data for that year was not nearly complete.

The PL hitters, team by team

In the 13 years worth of data, the Seibu Lions’ hitters have received more than their share of called balls each and every year. In their worst season, 2014, the Lions hitters were awarded balls on 67.5 percent of the pitches they took, just a little bit better than the league average. Since 2009, Seibu’s hitters average .97 standard deviations above the Pacific League mean, the best figure in Japan.

The SoftBank Hawks benefitted nearly as much from umpires calls as the Lions, averaging .79 standard deviations above the mean, and were above the PL average every year except 2009, the year before their current dynasty took flight, when they were less than .2 standard deviations below average.

The other four PL teams have generally been below average, with the Lotte Marines the best of that bunch, averaging just .01 standard deviations below the mean. The Orix Buffaloes and Nippon Ham Fighters have averaged being .47 standard deviations below, while the expansion Rakuten Eagles averaged .71 below.

The CL hitters, team by team

The answer to a trivia question I posted on Twitter when I first started looking at 2022 season data, about what team’s hitters far and away benefitted from umpires calls, nearly two standard deviations above the NPB season mean, was the Yomiuri Giants. The Giants were 1.66 standard deviations above the CL mean this year, and no other team was even close.

That led me to wonder if the Giants might be getting the best of umpires’ strike calls in all of NPB over a period of years, which didn’t seem that unreasonable, so with help from Mr. Westbay, I began looking at a larger sample and was surprised to see that Lions’ and Hawks’ have been farther ahead of the PL than the Giants have been in the CL.

Next behind the Giants have been the BayStars at an average of nearly one standard deviation above the mean. Coincidentally, the BayStars took fewer pitches than any other team in Japan in the study, which doesn’t come as a huge surprise in a park that favors all kinds off offense and traditionally hosts a large number of day games.

The other four clubs are not all that far behind, and it is nothing like in the PL, where there are two haves, and four have-nots.

It’s more about batters than pitchers

I know I go on about this a lot, but one of the reoccurring themes one notices in baseball stats is that the batter is by far the biggest single influence on how a plate appearance turns out. These data sets support that.

If pitchers were most influential, one would expect the variation in teams’ percentages of called balls and strikes to be higher among pitchers than hitters, but it isn’t, not by a long shot.

The median standard deviation of leagues’ batters’ ball percentages in Japan since 2009 is .0135, the standard deviations among the league’s balls percentages by pitchers during the same period is .00706, nearly half as large.

Not all teams’ pitchers are equal

When I first looked at the ball percentages by teams’ pitchers from 2022, and saw there was precious little variation from team to team, that they were all tightly clustered around the mean, so I focused on the batters.

But the variation among teams’ pitchers while smaller, is still interesting–when looked at over a period of years. That’s when you see which teams are more likely to get favorable calls on pitches that aren’t swung at.

In this table, average number of standard deviations BELOW the mean indicates a team that tends to get fewer balls called against their pitchers than the league average.

Since 2009, there have been 11 teams clumped around their leagues’ norms for the percentage of balls taken by opposing batters, and one outlier, the Yomiuri Giants.

Why this happens, and the conditions under which it happens are open to speculation.

Umpires are under a lot of pressure to get calls right. One umpire, who called balls and strikes in the Pacific League before moving on to the U.S. minors in a quest to umpire in MLB, said his kids would be harassed at school if he blew a call against some of their classmates’ favorite teams.

No one ever wants to blow a call, but I’m going to go out on a limb and suggest that there are some teams where some umpires are more likely to err on the side of caution when it comes to judgement calls against them.

Do some home teams tend to get far better treatment from the umps? I don’t know, but I expect to get the data for each pitch soon, and then be able to separate for example, the called Ball 4s from the called balls on 0-2 and the called strikes on 3-0.