The Strike Zone’s Still Dropping

Nothing groundbreaking here. The primary trend discussed has been discussed at length in other places, with far superior analysis. Here is one example! During the PITCHf/x era, through last season, umpires were granting more and more low strikes. Now we have most of a new season’s worth of data, and, guess what? Trend’s still alive. Trend’s still thriving. There’s never been a better time to be alive as a low strike, provided low strikes appreciate the company of others. We will, henceforth, focus on what I’ve elected to refer to as the zone of interest, because it is our present zone of interest:

zoneofinterest

The black box is an approximation of the average rule-book strike zone. The red zone of interest is somewhat arbitrary, but it more than gets the job done. Sometimes you don’t need to call on superior analytical techniques. Which is good for me, because I don’t know them. Data’s on the way! Thank you, Baseball Savant.

This is a graph with a lot of information. Don’t worry about consuming it all at once — we’ll break it down piece by piece. The four lines are labeled, because, why wouldn’t they be? If they weren’t, that would be a terrible graph!

zoneofinterest2

Red line first. This line shows the rate of called strikes within the zone of interest, with called pitches as the denominator. At the start of the PITCHf/x era, fewer than half the called pitches went as strikes. It reached about two-thirds in 2012, and now we’ve surpassed three-quarters. Relative to 2009, those pitches are called strikes now 60% more often. In numerical form:

  • 2008: 47%
  • 2009: 47%
  • 2010: 52%
  • 2011: 56%
  • 2012: 64%
  • 2013: 70%
  • 2014: 76%

There was a substantial leap between 2011 and 2012. Then the rate jumped another six percentage points, and now the rate has jumped another six percentage points. So, there’s no sign of a slowdown, here. Obviously, there’s a built-in maximum, but these called strikes are exploding. The lower part of the zone has never been kinder to pitchers, at least as far as we know.

Now the blue line. This shows the overall rate of pitches ending up in the zone of interest. This line isn’t nearly so fascinating. You’d think that, with the bottom of the zone opening up, pitchers would go there a lot more often. They have gone there more often, but not dramatically so. In 2008, the frequency was about one of every ten pitches. In 2011, it was about one of every nine. Over the past three years, the frequency has increased only four-tenths of one percentage point. We know that pitchers are throwing down more, and we know that hitters are looking down more, but this is a subtle thing, and the extra strikes aren’t being granted because the pitches are going there more. They’re just being granted.

Overall, this, of course, is significant. A lot of pitches go to that area, and the calls add up. The difference between 2014 and 2009 is right around 300 strikes per year per team. The difference between 2014 and 2012 is right around 125; the difference between 2014 and 2013 is right around 65. As people have reasoned, this is one of the factors behind the decline in offense. Between 2002 and 2009, there was no change in league strike rate or league first-pitch strike rate. Since 2009, the league strike rate is up a point and a half, and the league first-pitch strike rate is up a point more than that. In 2009, for every pitch thrown behind in the count, pitchers threw 1.9 pitches ahead in the count. This year, the ratio’s gone beyond 2.2. Pitcher-friendly counts favor pitchers in all ways, leading to more swings and to worse swings.

But let’s go back to the graph, and let’s consider the green dotted line and the gray dotted line. The PITCHf/x era captures two things: an era of more accurate umpire feedback, and the era in which we’ve come to understand pitch-framing as a skill. Are there more low strikes because of the umpires, or are there more low strikes because teams are more heavily favoring receiving ability?

I can’t actually really separate the two, if I’m going to be honest. But the green line averages the five best catchers in terms of getting low strikes, and the gray line averages the five worst catchers in terms of getting low strikes. Both lines have increased dramatically, but look at where the gray line has ended up: the five worst catchers this year are getting 61% called strikes in the zone of interest. The five best catchers in 2008 were at 64%. The league average in 2012 was 64%. The ceiling is still quite high, but the floor is rising.

As another way of considering this, the 2014 Blue Jays have gotten 63% called strikes in the zone of interest. That’s the worst rate in baseball, just below the Twins’ 64%. The Blue Jays would’ve been basically average just a few seasons ago. In a subtle area, things are continuing to change un-subtly.

Let’s consider every catcher with at least 250 called pitches received within the zone of interest, year to year. Each season, this gives us a sample in the dozens. Here are the standard deviations of called strike rates, as a percentage of the league mean:

  • 2008: 24%
  • 2009: 22%
  • 2010: 21%
  • 2011: 25%
  • 2012: 16%
  • 2013: 14%
  • 2014: 11%

Beginning in 2011, we observe less and less spread in league-wide performance. In 2011, the gap between the five best and the five worst catchers was 48 percentage points. This year, that’s dropped to 27. Some of what we’re seeing is greater emphasis on receiving low pitches with good technique, and some of what we’re seeing are just changes in umpiring, but at least in terms of low strikes these days, there’s a lesser difference between the best and the worst. So there’s less to be gained, relative to the average. A good low-pitch framer will appear less valuable in 2014 than he would’ve in earlier years, which is an interesting thing to think about.

Do we see anything that might resemble a cap? The highest rate in 2011 was 85% strikes, belonging to David Ross. The next year, it was also 85%, belonging this time to Yasmani Grandal. In 2013, Martin Maldonado came in at 88%. This season, Mike Zunino leads catchers at 90%. The ceiling is rising slowly, and it seems reasonable to assume it’ll be around, I don’t know, 92% or so. And the floor? For a handful of reasons, presumably, the effective floor is higher than ever. Catchers are taught certain skills, and they’re selected for certain skills, and there are more strikes being called low because of those reasons, and also independent of them.

People in the past have lamented the absence of the high strike. Baseball has responded by adding strikes somewhere else. People in the past have lamented the significance of pitch-framing technique. Baseball has responded by seemingly reducing the differences between the best and the worst pitch-framers. Did you know that everything around you is constantly changing? Even the floor that you’re sitting on. That floor is nothing like it was last week, if you think about it right.

We hoped you liked reading The Strike Zone’s Still Dropping by Jeff Sullivan!

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Jeff made Lookout Landing a thing, but he does not still write there about the Mariners. He does write here, sometimes about the Mariners, but usually not.

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Jim S.
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Jim S.

Another super job, Jeff.