This past weekend Danny Salazar recorded the 2,000,000th strikeout in MLB history. Given it took MLB until 1976 to reach 1,000,000 strikeouts, why did the league's second million strikeouts come so much quicker than its first?
There are several reasons. Up until 1969, MLB generally had 20 or fewer teams. The league didn't expand to 30 teams until 1998. Also, teams just played fewer games back then, as the 162 game schedule wasn't fully introduced until 1962.
But the obvious reason is that strikeouts are more common in the modern game, and are at an all-time high. Even on a per-game basis, since 2008 each consecutive year has set a new record for strikeouts. In 1948 when the league was at 500,000 strikeouts, there were only 3.64 strikeouts per game. By the time MLB reached 1,000,000 strikeouts in 1976, the strikeout per game rate had risen 32 percent and there were 4.83 strikeouts per game. Since 1976, the rate has risen 60 percent as there are 7.72 strikeouts per game this season.
It took MLB about 100 years to get 1,000,000 strikeouts and another 38 years to get to 2,000,000 strikeouts. If the current pace continues, reaching the next milestone will take even less time. Extrapolating last year's amount of strikeouts gives us about 27 years until MLB reaches 3,000,000 strikeouts. Though if the recent past is any indication, it could easily come even sooner than that.
[Reddit]