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The 22nd perfect game in major league history was unlike all but one that had come before. The Giants' Matt Cain struck out 14 Astros on June 13, matching Sandy Koufax for the most whiffs in a perfecto. Cain's big night produced the third no-hitter this month and the 16th in just under three years. This cluster of no-hitters is the product of a number of factors, none more important than this: Pitchers are throwing more strikeouts than ever.

A rising strikeout rate is the game's single most reliable trend. In 2012, 19.6% of plate appearances—nearly one of every five—is ending in a strikeout. That's a big jump even over last season's record pace of 18.6%. A decade ago, during the height of the power-hitting era, strikeouts accounted for 16.8% of plate appearances. The game has steadily evolved to select batters who trade contact for walks and power—call it take 'n' rake hitting—and hurlers who pitch to avoid bats. One of the lasting impacts of the sabermetric revolution has been to minimize the stigma attached to batter strikeouts—on balance, they are not worse for an offense than outs made on balls in play, and avoiding double plays cancels out the lost runner-advancement effects.

While Cain didn't need any help in his perfect game, the increase in K's is tied to another trend: the emphasis on bullpen specialization and shorter outings for relievers. In 1985, right at the end of the "fireman" era in which relievers were used in multiple-inning outings, the overall strikeout rate was 14%. The biggest inning for strikeouts was the second, with a rate 13% above the overall average. The K rate in the eighth inning was 4% above average; in the ninth it was 11% above average. Goose Gossage and his cohorts were having an impact but not distorting the game in the late innings.

Fast forward to 2012, and things have changed dramatically. The two biggest innings for strikeouts are the eighth and ninth, with rates 11% and 16% above the league average, respectively. Thirty years of treating relief pitching like a real job rather than an afterthought, of funneling live arms into roles that cover for limitations in endurance and pitch repertoire, have turned the ends of games into breezy affairs. In the era of relievers such as the Reds' Aroldis Chapman, a whopping 22.7% of batters in the ninth inning have struck out. (That figure was 15.5% in 1985.)

In an interesting twist, however, that spike in strikeout rates late in games isn't changing the distribution of run scoring. In 1985, 11.0% of runs were scored in the eighth inning; in 2012, that number is 10.4%. The ninth inning is even stranger: Despite the increase in strikeout rates and the evolution of the closer, a higher percentage of runs are scored in the ninth inning now (7.8%) than they were in '85 (7.4%).

So batters are striking out more because the payoff—walks and extra-base hits—is worth the cost. Pitchers are striking out more hitters in part because they're being used in roles that allow them to go for the strikeout and not worry about facing batters twice in an outing or having to throw 40 or 50 pitches. The reduction in balls in play makes it more likely that any one game, like Cain's, will produce lots of strikeouts, few balls in play—and a no-hitter. It's still possible to have a low-K no-no (the Twins' Francisco Liriano struck out just two batters in his in May 2011), but conditions are better than they have been since the 1960s for the kind of outing that makes history.