Thread by @dren_braves, I was asked by @nd4668 to see if umpires are worse this [...]

I was asked by @nd4668 to see if umpires are worse this year than prior years at calling balls and strikes, because it sure seems so!

I did some analysis, it's pretty cool, and it's going to take quite a few tweets to explain, so please stay with me.

First of all I want to thank @tangotiger and @darenw for their incredible statcast database which made it possible to do this analysis.

Home plate is 17" wide, or 1.4167 feet. A baseball is on average about 2 15/16" in diameter, so its radius in feet is 0.1224'. Statcast measures the location of the middle of the ball as it crosses the front of home plate (with 0 meaning right down the middle.

So if the middle of the ball is 1.4167' + 0.1224' away from the middle of the plate, then the edge of the ball will be right on the edge of the plate, and this is our side-to-side boundary for balls and strikes.

The top and bottom is a bit trickier, but fortunately statcast gives us a unique top and bottom of the zone for each hitter, so we can apply the same kind of logic to determine exactly what should be balls, and what should be strikes.

I pulled data for every called strike and every ball so far in 2021, and also for the entire 2015 season (would you have guessed that this is over four hundred thousand pitches? It took a while to collect this data!). I did not include any swings or contact.

First, I will answer Natalie's question. It turns out umpires collectively this year are better at calling balls and strikes than in 2015. I think it's safe to say they are better than ever. This year umps are missing about 8% of calls, and in 2015 they were missing 12.5%.

Here is another way of looking at it, in terms of what was actually a strike and called a ball, and vice versa. We see strikes are misclassified as balls more often, which makes sense because balls can be extremely far away from the zone, but strikes will always be pretty close.

Why are umpires better this year? Let me rephrase the question. Why are we noticing missed calls more now? Because of those little boxes they put up on the screen, I'd guess. Maybe umpires have sharpened their skills because they know fans can see in real time if they're right.

We are far from done, folks. Stay with me.

What about the Braves? Are they getting worse luck than other teams? Here is the data for Braves hitters in 2021 (misses when it's actually a strike help, misses when it's actually a ball hurt). Braves hitters are getting helped a bit more than avg, and are getting hurt the same.

Braves pitchers? Their strikes are being called balls less than avg (that's good), but their balls are being called strikes also less than avg (that's bad).

Ok now for my favorite part. Not all bad calls are created equal. For each missed call, I determined the distance to the nearest zone boundary. Then we can look at missed calls by how close it was. Here's 2021:

Note these are bucketed as a range, so 0 is actually 0-0.5", 1 is 0.5-1.5" and so on.

It's pretty amazing honestly that umps get 60% of calls right when they're less than half an inch from a boundary. The error percentage gets better as pitches get further away from a boundary.

Here's 2015, you can see improvement in each bucket.

Let's look at this another way. How often are calls missed up in the zone vs down, or inside vs away (adjusted for batter handedness obvs.) Here's 2021.

Up, down, inside, ok...HUH??? Outside??? WTF???

Well, umpires try to get as close to the plate as possible. Most (if not all) umpires set up right between the catcher and the hitter (I'm sure there are plenty of reasons they do this). So for outside pitches they're really just guessing if it's close bc they can't see.

Ok I think that's it for now. I wanted to see which umps are the worst but unfortunately that info is not available in the data I have. But we all know the answer anyway. Hope you enjoyed, thanks for making it this far, and go Braves and may the calls be ever in our favor.

ERRATA:

"if the middle of the ball is (1.4167'/2) + 0.1224' away from the middle of the plate, then the edge of the ball will be right on the edge of the plate

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