Click through to see all-time data on the average number of pitchers and hitters to appear for each team. Teams use a lot more players today than they used to.
Here are the average number of hitters and pitchers used each year per team. These numbers are calculated from the Pitching Encyclopedia and Batting Encyclopedia, taking the total number of hitters or batters appearing in a season and dividing by the number of teams n the league that year.
The black line is the ratio of hitters to pitchers for each year.
Keep in mind that these numbers do not distinguish between a regular player, part-timer, or late-season call-up. The hitters or pitchers may have appeared in many games or just one game.
Also, more than 100 years ago there were a number of cases of teams folding during the season so I wonder if the numbers there contain some errors--I would put less faith in the early part of the graph than I would the post-1900 numbers.
Comments and observations:
- In 2009, teams averaged 22 pitchers and 38 1/2 hitters per season. As you can see, these numbers are way up from historical values. In the 1880s, teams averaged about 4 pitchers and 15 hitters per season. (How mind-blowing is that?) Even as recently as the 1950s and 1960s, numbers were steady at lower values: 15 pitchers and 35 hitters per year.
- Note that the number of hitters took a huge dip in 1973. This is due to the introduction of the DH, meaning AL pitchers no longer batted and disappeared from the list of AL hitters. In 1997, when interleague play came along, the numbers went right back up. If I showed this same plot broken out by league, you'd see that the drop 1973-1996 was entirely in the AL.
- There are no significant differences between the NL and the AL for the pitchers per team plot.
- A few other blips on the graph are easily explained: The 1946 and 1955 blips were due to players coming back from WWII and the Korean War, respectively. The drop down in 1994 was due to the strike that wiped out September call-ups.
- Note that the ratio of hitters to pitchers has gradually declined over the years. In the 1920s, teams used about 2.5 times as many hitters as pitchers. By the late 1970s, the ratio dropped to 2-to-1. In the last couple of years, it's down to about 1.8. The advantage of looking at this ratio is that it tends to eliminate effects such as strikes, wars, and other things that affected games played across the league. The ratio tells us something about how teams use pitchers vs hitters. I suspect that the drop in the ratio comes down mainly to the fact that teams carry more pitchers these days. In the 1980s, most teams carried 9 or 10 pitchers on their staff. Nowadays, most teams carry 12 or 13 pitchers. More pitchers means more injuries and more replacements from the minors--in other words it seems to take 22 pitchers to occupy 12 spots over the entire season whereas it used to take only 16 to occupy 10 spots.
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