In the past few years, when interleague play was confined to certain segments of the season, Major League Baseball would issue these press releases about just how popular it was and how attendance spiked dramatically when the interleague series began. The clear impression they were trying to make was just how successful interleague play was as a concept.
Maury Brown at The Business of Baseball, however, crunched the numbers from and concludes that MLB’s enthusiasm about interleague play was really a lot of calendar-dependent noise:
While the rest of the season is yet to be played, the numbers compellingly show that interleague is not as popular as the past numbers have been said to be. It’s not that the “rivalries” aren’t popular, they are (they averaged 30,876 across the Rivalry Week in May this year), but rather balanced interleague throughout the season pulls in pretty much the same crowds as traditional interleague has.
None of this is to say that interleague should be removed. What it does say is don’t use those past numbers as propaganda to say how much more popular interleague is since it came into place in 1997. As the numbers now show, it’s pretty much a wash. Enjoy it for what it is, not some monumental popularity shift added to the regular season.
It was always notable that the big interleague p.r. push came after big weekend series between popular rivals, typically just as the warm weather finally showed up. Now that we have random Philly-Anaheim and Colorado-Seattle matchups in midweek during cold weather and everything else, we are seeing that baseball is, more or less, baseball.