Well, the results are in and the twelfth year of interleague play has been a landslide victory for the American League. So much for the pendulum swinging back to the senior circuit.
The three NL division leaders are a collective 16-29 against the AL. The three AL leaders are 34-20. Only three NL teams had winning records in interleague play (New York, Atlanta, and Cincinnati). Only two AL teams, both cellar dwellers (Toronto and Cleveland), had losing records against the NL.
Collectively, the AL was 149-102 against the NL for a .594 winning percentage. To put that in perspective, over a 162-game schedule that translates to a 96-66 record. That is equal to the best record in baseball in 2007 (Boston and Cleveland). That means that the average AL team is equal to the World Champs when they play the average NL team.
Consider that the NL has not won the interleague battle since 2003 and has only won it four out of 12 seasons. The best winning percentage for the NL in interleague games was .547 back in its first year, 1997. The AL has registered a .540 winning percentage or better in five seasons, including the last four straight.
The worst mismatch was .611 winning percentage for the AL in 2006. That equates to a 99-63 record over 162 games. No team has matched that record since 2005 (St. Louis & the White Sox).
And the mismatch is just getting worse.
The first eight seasons of interleague play witnessed four winning seasons for each league. From 1997 to 2004, the NL actually led the overall interleague series, 988 to 960, a .507 winning percentage.
It's the last four years that have skewed the results so badly. In that stretch the AL has had a .540, .611, .544, and .594 winning percentage in interleague play. They are leading the overall series, 576 to 431. That's a .572 winning percentage, or a 93-69 record over 162 games. That's a record that most teams would teams would drool over for a four-year run.
So does interleague suck worse now? If you ask me, it always has. It's fundamentally unsound. Forget the unbalanced schedule, the inelegance of arbitrarily applying the DH rule. Interleague play represents the last link in the chain that MLB has been building against such niceties as scheduled doubleheaders and in-season exhibition games.
Baseball crows over the Mets playing the Yankees, the White Sox playing the Cubs, and the other handful of same-city rivalries. Those series constitute the cherry on top of the sh*t sundae that is interleague play. However, historically same-city teams did play in-season exhibition championships, but those series got squeezed out as baseball went to 162-game schedules and tried to pry every dime out of every regular-season game.
Oh, and interleague play has impacted a ton of playoff races. I have to run the data but from 1997 to 2002, 19 playoff races were affected. And that was both leagues were on equal footing.