The Giants’ Matt Cain threw a perfect game Wednesday night against the Astros; it was the 22nd such game in major-league history and one of the most dominating performances among them, with 14 strikeouts.

Perfect games used to be rare, but in recent seasons we have almost come to expect them. Let’s look at the distribution of perfect games by decade:

1880s: 2
1890s: 0
1900s: 2
1910s: 0
1920s: 1
1930s: 0
1940s: 0
1950s: 1
1960s: 3
1970s: 0
1980s: 3
1990s: 4
2000s: 2
2010s: 4

Discounting the two in 1880 — pitched within five days of each other under different rules and conditions — there were two in the first decade of the 20th Century, and then just one from Addie Joss’ in October 1908 until Don Larsen’s in the World Series in 1956, a 48-year span.

It’s now been almost exactly 48 years since Jim Bunning threw one against the Mets June 21, 1964, and including that one, there have been 16 perfect games in that time period.

Commonplace? Perhaps not, but now we’ve seen five in the last three years. Run-scoring is down in general and we appear to be in the midst of a pitcher-dominated era. There have been five no-hitters already in 2012.

Prediction: there will be more perfect games sooner, rather than later.