Posted By:
Dave ReyYup, Barry, you're right -- only 12 unassisted triple plays in MLB history, with Wambsganss pulling the trick in the 1920 WS.
I'm not going to do the math, but it is obviously even more rare than perfect games.
Funny thing about unassisted triple plays: Half of the unassisted triple plays in MLB history happened between 1920-27.
Four of the other unassisted triple plays occurred from 1992-2003, which was, like the 20s, a period with a proliferation of offense.
My guess is the periods where offense is the dominating side of the game, like it was during the 20s and the 90s/2000s, the higher number of baserunners during these times, due to higher league batting averages and on-base percentages, provide more opportunities for the unassisted triple play.
By contrast, perfect game occurances seem to be fairly independent of overall ebbs and flows between offense and pitching eras -- though there were three during the 60s and a pair during the 00s dead ball period, when pitching was king.