Interleague Baseball Status Report

Bronx, NY, USA; New York Yankees catcher Russell Martin (right) celebrates with third base coach Rob Thomson (left) after hitting a walk-off home run against the New York Mets at Yankee Stadium. Mandatory Credit: William Perlman/THE STAR-LEDGER via US PRESSWIRE

We're a third of the way through the 2012 slate of interleague play, so it's time we evaluate the performance of each league. How are they measuring up?

You know who should care about whether or not one league is superior to the other? Baseball analysts. Analysts on the Internet or analysts who work for baseball teams, who have to worry about things like league adjustments when evaluating a player's performance. Outside of that, it doesn't matter. The All-Star Game pits one league against the other, but it pits only the best players against the best players, and it's one game. The World Series is supposed to match the best team in the American League against the best team in the National League, but it doesn't always feature the best teams, one team is only one representative, and the series is limited to four-to-seven games. If you aren't an analyst, you shouldn't be too concerned with league superiority or inferiority.

Yet people still are, because people are sports fans, and sports fans are irrational. In recent years, the AL has dominated the NL in interleague play, and this has caused fans of AL teams to become obnoxiously smug. In response, this has caused NL fans to be obnoxious back, with no one pausing to consider that they're getting all emotional over a league. Nobody roots for leagues. I did one time see a guy wearing a blank All-Star Game jersey who wasn't at the All-Star Game, but he was homeless. The most likely possibility is that the jersey was a donation. An alternate possibility is that this is something that happens to people who get emotionally invested in leagues.

Anyhow, I don't think it's worth becoming emotional over league performance. I do still think it's worth examining league performance for the sake of curiosity, and right now we're exactly a third of the way through 2012's slate of interleague play. So this seems like a good time to check out the results. Fans of the Nationals might assume that the National League is doing better, after their team went into Boston and swept the Red Sox. Fans of the Yankees might assume that the American League is still in control, after their team hosted its crosstown rivals and swept the Mets. How do their assumptions check out?

Over 84 interleague games, the AL has won 46 of them, good for a 54.8 winning percentage. In the history of interleague play, that would be the third-highest winning percentage ever, albeit a great distance behind No. 2 and No. 1. A year ago, the AL had a 52.0 winning percentage. The NL hasn't won at least half of the games since 2003. The full history:

Year AL Wins NL Wins AL Win%
1997 97 117 45.3%
1998 114 110 50.9%
1999 116 135 46.2%
2000 136 115 54.2%
2001 132 120 52.4%
2002 123 129 48.8%
2003 115 137 45.6%
2004 126 125 50.2%
2005 136 116 54.0%
2006 154 98 61.1%
2007 137 115 54.4%
2008 149 103 59.1%
2009 137 114 54.6%
2010 134 118 53.2%
2011 131 121 52.0%
2012 46 38 54.8%

We could stop there, but I don't want to, since the leagues have played just the equivalent of roughly half a full season. Over small samples, win/loss records can be deceiving. Over even bigger samples, win/loss records can be deceiving. What if we go beyond wins and losses and check out run differentials? That's probably going to be a better indicator of league performance.

So far in 2012, the AL has scored 410 runs, and the NL has scored 335 runs. For the American League, that's good for a Pythagorean 59.1 winning percentage. That's the second-highest Pythagorean winning percentage in interleague history, a hair behind 2008. The complete results:

Year AL Runs NL Runs AL Pyth%
1997 994 1007 49.4%
1998 1089 1078 50.5%
1999 1246 1374 45.5%
2000 1278 1233 51.6%
2001 1175 1175 50.0%
2002 1127 1097 51.2%
2003 1239 1267 49.0%
2004 1252 1210 51.6%
2005 1230 1056 56.9%
2006 1336 1115 58.2%
2007 1352 1172 56.5%
2008 1249 1014 59.4%
2009 1206 1061 55.8%
2010 1168 1098 52.8%
2011 1074 993 53.6%
2012 410 335 59.1%

Historically, the AL has won 52.3 percent of games, with the run differentials suggesting it should have won 52.9 percent of games. There's good agreement there, as we'd expect, and so it looks like the 2012 win/loss records aren't as lopsided as they should be. Over those 84 games, AL hitters have posted a .757 OPS, while NL hitters have posted a .697 OPS.

In the National League's defense, the Dodgers have played just three interleague games, and the Cardinals have played just three interleague games. But the same also goes for the Padres and the Brewers so that kind of gets canceled out. The real point in the National League's defense is: sample size. We're a third of the way through interleague play, which means we have another two-thirds of interleague play yet to go. Things could balance out, or things could even conceivably swing way in the other direction.

So we'll see where things go from here. It's too early to say anything conclusive about league superiority in 2012. According to the early indications, though, AL fans might just stay really annoying for at least another year.

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