The American League’s Still the Superior League

As I see it, there are three ways to determine which is better, between the American League and the National League. Those ways:

• The hard way
• The easy way
• The easiest way

The easiest way is to just pick one and stand by it. Think the National League’s better? Declare as much and refuse to give any ground, no matter the evidence. You have made your determination!

That leaves two ways to do this with actual math. The more complicated way is to look at the performances of players who’ve switched leagues, and compare those performances to expected performances. That’ll get you somewhere, but that’ll also cost you a good amount of time, most probably. Thankfully, there’s an easier way that works just fine. Want to know which league is better? Look at how each league has performed against the other league! This is the 18th year of interleague play. It’s as old as Brady Aiken. It’s not new anymore — it’s old enough to join the army — and we can make use of the data it provides.

Of course, the season isn’t over. Of course, not every team in each league plays every team in the other league. So of course, any information you get out of this is going to come with its attendant uncertainties, but when life provides an easy way to get at the answer to a question, you seize it without looking back. In 2014, we’re 190 games into the slate of interleague play. AL teams have won 102 games and lost 88. They’ve outscored NL teams 845 – 799. The AL leads in OPS differential by 14 points. Based on the evidence we have, the AL is the superior league, and I think many of us have gotten used to this.

The NL hasn’t won half the games since 2003. The NL hasn’t outscored the AL since 2003. The NL hasn’t had an advantage in OPS differential since 2002. Below, you can look at a couple charts, showing the history of the three statistics.

I should note that I used OPS instead of wOBA out of convenience — data’s been pulled from Baseball-Reference, and Baseball-Reference uses OPS instead of wOBA. I can’t imagine wOBA would tell a meaningfully different story, as OPS gets the job done, as strange as it is to consider.

Depending on the stat, you can spot some different eras. By winning percentage, the AL’s had a pretty firm lead for a decade. By run differential per game, things have calmed down since an AL peak between 2005 – 2009. By OPS differential, it’s been a more recent calming effect, really kicking in last season. Not coincidentally, last season, the Astros moved from the NL to the AL, and while the Astros have lately gotten a bit better, they were terrible in 2012, they were terrible in 2013, and they were terrible to start 2014. Leagues are massive entities, but the Astros evened the field a little bit. Moving a team was long overdue, and the Astros weren’t going to be terrible forever.

It used to be, when people would talk about the AL’s advantage, they’d make sure to point to payroll inequality as a factor. For years, the average AL payroll was higher than the average NL payroll, and spending, of course, correlates to success. But this year, the average NL team is outspending the average AL team by about three million dollars or so. So a leg or two has been kicked out from under that argument, but of course, this could be more detailed — what we’re lacking is comprehensive service-time information. Not every player’s in position to make free-agent money, and so this might still be a meaningful point.

Besides the Astros point, and the payroll point, how might the NL be making up some ground? Perhaps the NL is now the better defensive league. According to UZR, since the start of 2013, the NL has been better defensively by almost 130 runs. And according to Defensive Runs Saved, since the start of 2013, the NL has been better defensively by almost 800 runs. I don’t know how to explain so big a difference — it probably has something to do with how shifts are treated — but we can at least say that the NL is better in the field, and it might be way better. This would be one reason the difference between the leagues has settled down.

There’s also the Dodgers factor. And there’s the declining-Yankees factor. Baseball isn’t controlled by the Boston/New York rivalry the way it seemed to be several years ago, and that’s helped to even the playing field, even though the situation is still slightly tilted in the AL’s favor. An explanation for the continued superiority could come down to front-office superiority, but that’s a difficult thing to prove. Anecdotally, one of the leagues has Billy Beane and one of the leagues has Ruben Amaro, but that’s not very scientific.

The long and short of it: for another season, it would appear that the American League is stronger than the National League. This is a trend that’s kept up for years, but to the NL’s credit, the two leagues aren’t as different as they were a few years back, and it seems like things might be balancing out some. This season there’s no AL payroll advantage, and it stands to reason this ought to be pretty cyclical. Within recorded history, the NL has won the majority of interleague contests in a year. That’s probably not going to happen in 2014, but maybe next year or the year after that. So, something to look forward to, fans of the National League. I don’t know why there would be fans of leagues, but I don’t know why there would be fans of American Authors so I’ll just assume some are out there and leave it at that.