MLB Statistics – Why So Many No-Hitters?

Matt Cain pitched a perfect game for the Giants this week.  Some people have been wondering “WTF?  Why are there so many no-hitters and perfect games recently?”

Overall league batting average is down this season, compared to last season, by about 0.005 to 0.01.

It’s a nonlinear relationship.  If overall batting average decreases by a little, the odds of a no-hitter or perfect game increases dramatically.

Suppose that overall league batting average is x.  Then, the odds of a no-hitter are approximately (1-x)^27.  If you want to calculate the odds of a perfect game, use on-base percentage instead of batting average.

Using that formula, here are some details

League Batting Average Odds of a no-hitter
0.280 0.014%
0.270 0.020%
0.260 0.029%
0.250 0.042%

Notice that a small decrease in batting average leads to a huge increase in the odds of a no-hitter.  If overall batting average decreases from .270 to .260, then the chance of a no-hitter increases by nearly 50%!

Usually, when batting average decreases, MLB will change the rules to favor batters, either by lowering the pitcher’s mound or shrinking the strike zone. Until then, there will be more no-hitters, due to a decline in batting average.

There’s been an “explosion of no-hitters” recently, due to a decline in overall batting average. It’s a nonlinear relationship. A small decrease in batting average leads to a huge increase in the odds of a no-hitter

2 Responses to MLB Statistics – Why So Many No-Hitters?

  1. That’s a good point about how a small decrease in overall batting average leads to a significant increase in no hitters, but it then begs the question as to why there has been a decline in overall batting average. I think you touched on it and I think that umpires have expanded the strike zone the past couple of years.

    • Maybe there’s lower batting average because the players stopped taking steroids?

      I’m an expert on the Math analysis. I don’t know much about baseball.

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