Travis asked this question yesterday in his post (what's the deal with 100 pitches?):
In 1988 (the first year full league pitch data is available) we saw 134 pitches/game/team and 21708/year/team. And in 2009 we saw 147 pitches/game/team and 23814/year/team.
So 2009 teams threw about 2100 more pitches than 1988 teams (though nowadays it's spread out over slightly more pitchers). What's perhaps more interesting (than why is there such a difference between the usage of modern pitchers vs. 50 years ago) is why there is such a vast difference in only the last 20 years. The DH, lower mound and PEDs all existed in 1988, just as today. What could make for that 2100 pitch difference?
I did some digging, and I think I found the answer.
Think about how the game has changed over time. I'm not necessarily talking about big changes, like moving the pitcher's mound to 60 ft 6 inches or adopting the DH rule. I'm talking about small, gradual, philosiphical ones.
There was a time (as purists say, "the good old days") when striking out was heavily stigmatized. Entire seasons passed without a single player whiffing 100 times, and it wasn't until the 1963 season that somebody managed to strike out, on average, more than once per game (by comparison, 7 players struck out at least 162 times in 2009). A strikeout could not advance the runner (except in rare circumstances), and so they were viewed less favorably than, say, the sacrifice bunt.
Although less prevalent these days, many still believe correct baseball strategy dictates a sacrifice bunt when there's a runner on first and no outs, especially in "late and close" situations. Teams also used to steal bases far more frequently than they do today. You could arguably call the period from 1965-1994 "the golden age of the stolen base" in the modern era, as 75 of the 100 highest single season stolen base totals recording during the live ball era occurred during that 30 year period.
Today, however, attitudes are very different. Teams strike out more frequently, sacrifice less often, and steal (and get caught stealing) less often. The differences from year to year are small, but in chart form, they're very noticeable:
(note: caught stealing statistics were only fully recorded beginning in 1951)
All three of these things directly impact pitch counts.
Think about strikeouts. A hitter is able to ground out, pop out, or fly out on the first or second pitch, but he cannot strike out until at least the third pitch. Taking the global view, at-bats which result in a strikeout will, as a whole, require more pitches to be thrown than at-bats which result in some other type of out. And boy, have hitters increased their propensity to strike out! In 2009, a whopping 18% of plate apperances ended in a strikeout. Compare that to any point in the past; up until the early 1950s that number was consistently under 10% and even into the early 1990s it was usually under 15%. Sacrifices and times caught stealing have the opposite effect. They both result in out being recording without the pitcher having to throw many (or any) pitches. Think of them as free outs, or at the very least, cheap outs, that pitchers have been getting less and less often in recent years.
Look at it this way. Imagine an average pitcher, with an average strikeout rate and average pickoff move, facing average hitters. If he faced 1,000 batters in 1988, 147 of them would have struck out, while about 10 would have sacrificed themselves at the plate and another 9 would have been caught stealing. Compare that to 2009; 180 would have struck out, while only 9 would have sacrificed and only 6 would have been caught stealing.
More strikeouts means fewer grounders, popups, etc., which means the pitcher must weather himself through more 3+ pitch at-bats. And fewer sacrifices and times caught stealing means more real at-bats against hitters who are trying to reach base.
I think that's why it takes more pitches to get 27 outs these days.