Let’s Take Another Stab at Unpacking the Rising Strikeout Rate
If you are a regular FanGraphs reader, chances are that you’re aware of the rise in strikeouts across the majors. At this point, bemoaning the rise in strikeouts is an essential component of the baseball media apparatus. Every season is accompanied by pieces on the subject. I found this type of article going as far back as 2013, and they have been especially prevalent in recent seasons. It seems to be a rite of passage to put out a piece on the increasing strikeout rate, so as a newly minted member of the baseball writing community, here is my entry in the genre.
For context, the league-wide strikeout rate has increased every season since 2005, when it sat at 16.4%. In 2021, that figure has risen to 24.1%. That is a 47% increase in 16 seasons. Not only has the strikeout percentage monotonically increased, but the rate at which it is increasing is growing. From 2005-09, the rate increased by 9.7%; from 2010-14, 10.3%. In the most recent five seasons, the strikeout rate increased by 11.6%.
The question is always who and what is driving this phenomenon, and the answer is almost always “well, there are a few factors at play.” One angle that I thought has been under-researched is hitter behavior with two strikes. You may have heard your favorite local newspaper columnist bemoan the idea that hitters do not have a two-strike approach anymore, that all they try to do is hit home runs, which has led to all the strikeouts. Of course, this type of thinking is reductive, mostly because it does not even consider the role of the pitcher. Nevertheless, many have discussed two-strike results, though more anecdotally than quantitatively. So let’s investigate this aspect of the strikeout rate problem first. The following is the strikeout rate and wOBA in plate appearances that reach two-strike counts in the Statcast era:
| Season | K% | wOBA |
|---|---|---|
| 2015 | 40.4 | .240 |
| 2016 | .41.1 | .243 |
| 2017 | 41.5 | .247 |
| 2018 | 42.2 | .241 |
| 2019 | 42.8 | .247 |
| 2020 | 43.2 | .245 |
| 2021 | 44.6 | .229 |
Like the overall strikeout rate, the strikeout rate in these plate appearances is monotonically increasing but much more slowly. Year-over-year, the increase never exceeds 2% besides this season and 2020 (about 3%). I will note we are only about a month and a half into the season and given the weather, league offense is at its nadir, so I would expect this to regress some. wOBA with two strikes has jumped in the Statcast era and this season so far has stuck out like a sore thumb. The weather caveat applies here also, as does the caveat that we are dealing with only a fraction of the plate appearances in 2021 versus all other seasons besides 2020 (for obvious reasons). This information seemingly debunks the awful two strike approach theory, at least within the defined time frame. Hitters are barely striking out more when they get to two strikes and their overall performance has not changed much season-over-season, 2021 notwithstanding. If we dig further into two strike behavior, the idea that hitters have drastically changed when they are confronted with two strikes does not track:
| Season | SwStr% | CS% | Swing% | Chase% | BBE% |
|---|---|---|---|---|---|
| 2015 | 13.1 | 4.4 | 59 | 45.8 | 23.8 |
| 2016 | 13.3 | 4.4 | 58.8 | 44.7 | 23.2 |
| 2017 | 13.5 | 4.4 | 58.5 | 43.6 | 22.8 |
| 2018 | 13.8 | 4.5 | 58.6 | 43.1 | 22.6 |
| 2019 | 14 | 4.4 | 58.4 | 43.5 | 22 |
| 2020 | 14.1 | 4.6 | 57.5 | 42.8 | 21.8 |
| 2021 | 14.4 | 5.1 | 58 | 42.1 | 21.6 |
I will note that the chase rate calculation is based on my own filtering of the Statcast data from Baseball Savant. The swinging strike rate has increased every season and the rate at which balls are put in play with two strikes has decreased every year, which gives some credence to the complaint about hitter behavior. I would argue the changes are so small, however, that drastic claims about today’s players are not warranted. We are talking about 1.3 percentage points in terms of swinging strike rate, and 2.2 percentage points in balls in play rate from 2015-21. I do not think anyone without access to this kind of statistical information can really tell the difference between those figures when watching the game. The swing rate with two strikes has been very stable in this era. In terms of chase rate, batters have become more discerning, which can only be construed as a positive development, assuming we believe it’s better to have fewer strikeouts.
Interestingly, the rate of called strikes as a percentage of total two-strike pitches has seen a noticeable jump in 2021. Devan Fink wrote about how pitchers have become more aggressive throwing the ball in the zone this season with the advent of the new ball. I would imagine this is the impetus for the growth in the percentage of strikeouts via the called strike.
Overall, the differences in two-strike performances between seasons do not seem substantial enough to explain the acceleration of the strikeout rate growth. Maybe it is not batter performance in two strike counts, but instead a notably higher percentage of total pitches being thrown with two strikes?
| Season | 0-0 | 0-1 | 0-2 | 1-0 | 1-1 | 1-2 | 2-0 | 2-1 | 2-2 | 3-0 | 3-1 | 3-2 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 2015-20 | 25.8 | 12.8 | 6.5 | 10.1 | 10.2 | 9.5 | 3.5 | 5.3 | 8.1 | 1.1 | 2.2 | 4.9 |
| 2021 | 25.5 | 12.5 | 6.7 | 10.2 | 10 | 9.5 | 3.5 | 5.3 | 8.3 | 1.2 | 2.3 | 4.9 |
There is basically no difference between 2021 and the preceding five seasons combined. The count-based run values are more of a mixed bag with no discernible trend.
| Season | 0-0 | 0-1 | 0-2 | 1-0 | 1-1 | 1-2 | 2-0 | 2-1 | 2-2 | 3-0 | 3-1 | 3-2 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 2015-2020 | 0.009 | 0.008 | 0.018 | 0.008 | 0.001 | 0.016 | 0.025 | 0.002 | 0.003 | -0.009 | -0.008 | 0.013 |
| 2020 | 0.024 | -0.079 | -0.067 | 0.176 | 0.047 | 0.142 | 0.357 | 0.002 | 0.056 | -0.15 | -0.121 | -0.098 |
Two strike performance changes does not seem notable in recent vintage. In fact, the swinging strike rates in all counts have effectively increased at the same rate across all counts.
The last thing I investigated was looking at pitch types and seeing if any groups of pitches are more responsible for the rate of whiffs than the others. Here there are more interesting trends.
Neither breaking pitches nor offspeed pitches have seen much of an influx in swinging strikes. Hitters have struggled more with fastballs, on the other hand, in all situations. (Another hat tip to Devan Fink, who wrote about the unusually large increase in fastball velocity in the month of April this season.) Pitchers’ fastballs are becoming tougher to time-up and now that they are becoming more aggressive throwing the ball in the zone, they are inducing more swinging strikes with those pitches.
The league’s two-strike approach does not seem to be having an outsized effect on the rise in strikeouts, at least in this most recent era of baseball. There are small upticks in a few relevant metrics, but more of the increase has to do with swings and misses in all counts, especially on fastballs. This count-based analysis yielded similar results to an excellent piece from Chet Gutwein here at FanGraphs. He found that not only has the league’s swinging strike rate on fastballs increased more relative to other pitch types, but fastballs high in the zone were mostly to blame due to the continuing growth of velocity and, as a consequence, spin rate.
As the league tries to address the issue of fewer balls in play now and in the future, finding a way to combat the rise in pitcher velocity should be one of the first items on the docket. The fact that pitches are moving more than ever does not appear to be as large a factor, given the changes in whiff rates on breaking and offspeed pitches. Moving the mound back, which will be implemented in the Atlantic League this season, and giving hitters more time to react seems like a good start. After parsing through the two strike data, it seems like rectifying the lack of formidable two strike approaches across the majors is not the silver bullet many believe. Digging further into the data by pitch type in all counts, the main issue is rising whiff rates on fastballs, which Chet Gutwein opined on in his own piece I referenced above. So maybe combating velocity is the elusive silver bullet? Without a relatively controlled experiment we cannot say for certain. But we can say that hitters being criticized for forgoing any semblance of a two strike approach and placing the blame on them for the rise in strikeouts is most likely a futile exercise.
Carmen is a part-time contributor to FanGraphs. An engineer by education and trade, he spends too much of his free time thinking about baseball.
Interesting!
Just via observation and anecdote, these conclusions do track. In the mid teens, the more analytically inclined teams started noticing that high velocity, high spin fastballs up in the zone (and even some sliders and curves that land at the upper edge of the strike zone, previously a completely verboten type of pitch, a pure mistake) were extremely effective against a generation of hitters that had been trained to elevate low fastballs. It took a few years for the concept to to be implemented in minor league development, and for other organizations to notice, but now it’s becoming quite uniform. Another factor that contributed was the league wide trend for hitters to stand close to the plate, which took away pitchers’ refuge on the outside corner. So it made sense for pitchers to switch to working up and down rather than side to side.
Is there a natural response without rules intervention? Maybe not. Guys are pretty near the absolute limit of the human eye and nervous system’s ability to process information and adjust. For 140 years the structure of baseball has allowed responses to each innovation, but it’s not an unlimited capacity.
The outside corner refuge is also umpire driven IMO. I’d guess about half the umps regularly call pitches a few inches (or even further) outside as strikes.
Any discussion of leaguewide changes in strikeouts is incomplete without discussing umpire strike zones and how they changed over time (sometimes, but not always, in a conscious way).
tung, you have hit on a key component of this discussion. I don’t know if I am the oldest regular participant in this very knowledgeable blog but at 79, and an avid fan, I have seen what you speak about first hand. In the 50’s, my teenage years, baseball was THE game and the zone was several inches higher then. The high hard one was the pitch of choice. That continued and finally culminated in the 1968 season and while that was the nadir of hitting averages didn’t return until the late 70’s. Right about this time the zone suddenly changed. in an instant the belt became the top of the zone and anything that didn’t hit the ground, realistically mid shin, was now a strike. The high fastball disappeared overnight because hitters simply knew they didn’t have to worry about it being called strike. Naturally the pitching fraternity changed as well and for the next 30-40 years the pitching was dominated by sinker-slider guys who kept everything around the knees. The hitters were complicit in this because there weren’t many, or even any, of the hitting coaches who understood bat path through the zone or launch angle and spin. Hitting played right into the hands of the pitchers as both sides were trying to keep the ball on the ground. Somebody had to be wrong and it was the hitting that was taking the wrong approach. Getting back to your comment there was absolutely a decision made by the umpires to lower the zone. I will always believe this was a power play orchestrated by Richie Phillips, the head of the umpires organization beginning in 1978. Finally, around 2014 the hitters learned that the Laws of Physics govern the flight of a baseball and the talented players quickly saw the logic, followed by the results, of hitting the ball in the air and some of the dinosaurs in the hitting coach fraternity were asked to leave and the home run, and the K, took over the game. As this happened the pitchers were forced to again start throwing the high heat and the zone has moved upward as umpires have accepted this latest change. When added to the dramatically increased velocity that virtually every pitcher now employs it has been getting more and more difficult for anyone, other than a few elite players, to make anything resembling consistent contact.
Look at contact rates in the zone and out of the zone year over year. I think you’ll find your answer.
Interesting if broken down by pitch type. For me, it’s the elevated FB. 99% of swings & misses at FB’s up are underneath the ball. Umpires have raised their zones. P’s, especially those with carry & high spin are pitching up more with their high spin 4 seam fastballs. Therefore more swings & misses with two strikes. On the flip side IMO many successful two strike hitters adjust. They make subtle physical adjustments(IE. wide base no stride) & they change their approach..(5 iron vs. driver) & cover a smaller zone vs. trying to cover the SZ + which leads to more chases.
jw
Good work!
Anything that pushes back on “Local Man Rants; Media Creates an Unexamined Narrative” is appreciated around these parts!
The lack of 2 strike approach has been a complaint for essentially the entirety of the statcast era. It is not surprising that you found no change in 2 strike approach across that period. I suspect that you would need to go back 15 to 20 years to watch a change in 2 strike approach develop across the league, if in fact such a change does exist. I’m not saying your conclusion is wrong but that you have provided insufficient information to refute the hypothesis that hitters have changed their 2 strike approaches.
I agree the two-strike approach is not the culprit, but I don’t think I’d agree the two-strike data refutes the hypothesis. If batters are striking out more frequently when at-bats get to two strikes and wOBAs are remaining steady, then hitters are doing more damage when they do connect, which is consistent with a go-for-it! two-strike approach.
The fastball data is much more convincing, however, and suggestive of a hybrid approach to finding an effective remedy. The current equilibrium baseball has reached has, to me, several negative components: less emphasis on starting pitching, more emphasis on power hitting, a parade of relief pitchers, and increased chances for pitcher injury (higher velocity = higher chance of injury, though the data is probably inconclusive thus far). Limiting the number of pitchers a team can carry, more effective enforcement of foreign substance rules, and implementing the pitch clock all seem like things worth trying.
I am sure there are a number of micro explanations that can help explain it, such as the ones highlighted in this article. But isn’t the macro explanation that strikeouts are just more acceptable for hitters today than they were 15 years ago? There is less incentive to avoid striking out than there was in 2005 and it has been a gradual decay as advanced analytics have decreased the negative impact striking out has on a player’s value. That macro trend has governed everything else.
On a personal note, I love dominant starting pitching and have enjoyed seeing some of these dominant strikeout performances from a new stable of dominant starters. But I would be lying if I said that overall it is less enjoyable to watch the game with less balls in play, especially when players seem increasingly less affected by striking out more.
Anecdotally, I noticed how many strikeouts the Braves had in the recent 3-game set with the Blue Jays (36 in 3 games). Dansby Swanson in particular typified many of their hitters’ approaches during the series: K, K, K, K….home run…K, K. It’s like you either crank one out or go down trying to.
Added to that, there’s a longer discussion piece from Tim Kurkjian on ESPN regarding the ever-rising K rates in the game today. Has a lot of “back in my day” from the likes of Nolan Ryan, Kevin Seitzer, Reggie Jackson, etc, but is a very worthwhile read.
I’ve mentioned this before, but like I said I respect peoples’ enjoyment and the value people get in stats. I respect everyone believing a firm believer in stats in order to assess future performance. I even understand most (but not all) decisions made in the game because of stats and why things are the way they are. I even understand what probability is, it’s the likelihood of a particular situation or instance occurring. I just see statistics as only real value in terms of predictions in other lines of the world like the medical field and politics. I just feel stats that are accumulated predicate much less so on ability in other lines of the world than they do in sports, because there’s not as many moving parts to consider in my view, which makes me skeptical of any stat. It doesn’t exactly take a lot of in depth stats and analysis to see that global warming is happening and feel confident in those stats, but in sports with all the moving parts, mechanics, and intricacies that exist it’s hard for me to buy into them to where I would feel confident trusting in the numbers alone.
I just feel if I can see evidence using the eye test of particular things hitters and team do that are not covered by stats and I accurately predict a team will win the World Series at the start of the season despite the percentages, why shouldn’t I feel more trust and confidence in myself in terms of what I saw than what the percentages actually say? After all I defied the predictions! I wasn’t wrong! Yes I will be wrong again several times, but how do we know with 100% certain human judgment and the eye test is a lower percentage in every long term instance? How do we know we can’t inch any closer to 100% with our predictions, without it obviously being 100% if we switched between using a combination of stats and the eye test? How do we know that doesn’t work? I realize we will never get close to 100%, but can we actually prove for certain the contrary that only stats ever work and that the eye test can never ever have any value to where we can build enough confidence to assert the stats only ever matter?
I’m not here looking to sway anyone’s opinion on the value of stats. I’m not even saying or proposing ignore stats or discredit stats. I’m just proposing an alternative view point of instances where the eye test can have credence. I just think if someone sees something, they are not trying to be oblivious of long terms stats accompanied by larger sample sizes or the outcomes percentage that come with them, they just have see something that gives them a reasonable explanation why something didn’t work out if a hitter fails. I mean how would a hitting coach be able to help a hitter if he only looked a his player’s stats and never bothered to ever watch what his hitter did in his at bats? The hitting coach obviously feels it’s important to analyze each at bat he watches or he wouldn’t bother to use any sort of eye test when the stats compiled from scouts are readily available to him all the time to analyze what his hitter may be doing wrong. Now someone might say, “well he’s looking for any discrepancies in what scouts have compiled from what they saw over what he sees” ok, but why not trust your own judgments of what you see over what a scout sees? Does a hitting coach really believe that a scout who’s likely never coached before to analyze better in terms of what they are looking at then a hitting coach himself?
How do long term stats figure into if a hitter excels at getting a base hit off of a pitcher’s pitch on the outside corner or if he fouls back a lot of pitches right down the middle or if a hitter is taking a lot of pitches right down the middle? How do we factor into stats the kind of batting stances hitter’s have and the likelihood one stance produces more success than another in the long term? What about a hitter’s level of vision, and statistical outcomes that come along with that level of vision? I mean after all, a hitter with 20/20 vision is more likely to recognize pitches better than someone that doesn’t have 20/20 vision? Am I correct? I just feel stats don’t cover this enough to my liking to actually see enough value in the advanced stats that already exist over the eye test that I can currently use.
I just feel not enough is covered in stats to feel more confidence in them over the eye test.
I mean look at Gerrit Cole and the 1-0 game he pitched against the Rays. The statistics say take him out after 100 pitches, did the Yankees listen to the stats? Of course not and he did fine.
Very much agree with this. Many stats that were derived for the purpose of predicting future value have been overused to explain past performance. And I think the pendulum needs to swing back a bit. A good example to me I see often is a pitcher’s FIP overtracking his ERA for long multi-year stretches. In the rearview mirror, we should really be relying on ERA as a better judge of past performance, whereas FIP would be used to predict how much better results they could have received to help measure future value. But at some point we need to not parse out past performances too much in a way that erases actual results, especially when it discredits players accomplishing the ultimate goal of reducing or producing runs.