The Decline of the Doubleheader

As we all know, doubleheaders are a rarity these days, confined to make-up games. I was curious about how their frequency has declined over the years. A quick munge of the Retrosheet game logs produced the graph below. Note that this is percentage of dates that were doubleheaders, not games that were doubleheaders.

Looks like the frequency went up in the 1930s–don’t know why. The spike during WWII must be due to the travel restrictions. After the war it’s a pretty linear decline to 1990, where it bottomed out. The reasons for the decline certainly include the following:

• Air travel reduced the need for travel days.
• More night baseball.
• Owners figured they ended up losing money on twin bills.
• Players don’t like ‘em.