Why So Many No-Hitters?

Josh Wright —  6 July 2010

I read a really interesting column in Sports Illustrated, full of anecdotal accounts from players, managers and well-informed baseball observers, explaining the perceived dramatic uptick in no-hitters so far this season.   With four no-hitters in a short period of time in the 2010 season, the most popular explanation has been steroids.  That was SI’s answer (see also here, here).  I’ve always been a bit puzzled by the steroid explanation because casual empiricism suggested that pitchers were benefiting from steroids too.  And less casual empiricism from Justin Wolfers — who took on the case of Roger Clemens — suggested the same thing (see also here).  Of course, its perfectly plausible that steroids benefit hitters more than pitchers  (but see here).  And the MLB home-run rate is low.  Also, there could be other explanations for an increase in no-hitters and/or perfect games, e.g. better defense.

Anyway, none of this is an attempt to provide a definitive answer.  Or even a not-so-definitive one.  The column just got me wondering about what the data look like.  I thought I’d show a picture that I put together based on the data from this CNN/SI column on the top 16 seasons for no-hitter frequency after 1901 to put things in context.

These data certainly are not conclusive.  But they seem to suggest that while 2010 is a good year for pitchers, and for no-hitters (the third highest no-hitter frequency at .18% thus far this season; the two best no-hitter seasons were 1908 and 1917 at .24%), the data also suggest that 2010 is not that unique.  Ten seasons since 1901 have had no-hit frequencies ranging from .15% to .18%.  Notice also that there are several high no-hit seasons from before the steroid era.  One explanation that is frequently tossed around is the increasing strike-out rate.  See below (the red line on top is strikeouts/9 innings):

No answers here.  Like most empirical questions, it is difficult to disentangle the determinants of the increasing strikeout rate.  But it strikes me that this trend at least as components that are entirely unrelated to the steroid era changes, e.g. changes in strategy or reduced stigma associated with striking out as it becomes an acceptable cost of hitting more home runs.  I’m no baseball expert.  But there seems to be some interesting stuff here.  Why has the strikeout rate increased so consistently over time?   How big of a deal was the steroid era anyway, in terms of relative performance of pitchers and hitters?


4 responses to Why So Many No-Hitters?


    The no-hitters could just be a statistical anomoly – but I’m skeptical after how we ignored the real causes of the home run boom. Just curious if there are any theories that would explain why this isn’t an anomoly (perhaps umps are systemicaly expanding the strike zone this year?).


    Ted: Good stuff! Thanks.

    Antitrust Guy: Indeed. I kind of thought that the first part of the post in which it is pointed out that this year is on the high-end, but certainly within the realm of “normal” outcomes, was about making the point that this could just be a typical draw from a distribution that hasn’t changed over time.

    But, yes, apparently, there is at least some reason to think that there are factors influencing pitcher/hitter outcomes. Others have raised a number of theories about why pitchers might have improved relative to hitters (resulting in increasing strikeout rate, lower batting average, lower HRs, lower ERAs even if not more no-hitters), such as changes in the game itself, steroids, etc.

    But I don’t know, in response to your question, why one would be interested in talking about explaining variance in the no-hit frequency rate without controlling for possible explanatory variables.

    antitrust guy 7 July 2010 at 1:00 pm

    Is there any reason to think the no hitters are something other than a statistical anomaly? That is, even if only 1/1000 games results in a no hitter, you still have a some chance of “bunching” of those instances. Don’t we have to reject that hypothesis before looking for explanations?


    There are a few factors in the strikeout rate increasing over time:

    1) Relief pitchers. Pitchers used to pitch 300 innings a year regularly. This meant (a) pacing themselves to not throw hard all the time (esp. in the first third of the century—you’ll see pitchers in interviews expressly stating that it was important to not give it your all every pitch); (b) more pitcher injuries, reducing the talent pool; and (c) pitchers pitching tired, losing several mph off their pitches. Now, when every pitcher is well-rested, when you rarely see starters for more than 100 pitches, when teams carry eleven or twelve pitchers instead of eight or nine, there’s a fresh fireballer every inning. There may be more strikeouts now than ever before–but the top season strikeout records are all from a generation ago or more. Complete-game totals and average innings/start and IP/year have been on a downward trend throughout MLB history.

    2) As you note, an increased willingness to swing for the fences on two-strike pitches. 100-strikeout seasons for batters used to be extraordinarily rare. Now just about every team will have a batter hitting the century mark.

    3) An increased understanding of the value of taking pitches. This increases strikeouts, but it also increases walks, and gets the starting pitcher removed much faster. (Amazingly, though the top teams all put a lot of value on this, this new conventional wisdom still hasn’t filtered throughout the majors.)

    There’s a 1969 rule change that lowered the mound and changed the size of the strike zone, which is why you see that blip in the data.

    Hard to know where steroids fit into all of this. Sammy Sosa was on the juice, but he was striking out a lot, too, and there were surely pitchers whose career was helped by steroids.