Like Democrat or Republican or Star Trek or Star Wars, American League or National League is one of those furious debates. Ask it out loud in a room full of people, and there will be raised voices.
Goodness knows we all have our biases when it comes to the AL vs. NL debate. In the interest of full disclosure, I know I do. I used to live in New England and now live about 20 minutes outside of Oakland, so I've never really had a choice but to be an American League guy. It's in my blood.
But while I may practically be programmed to say the American League is better than the National League, I also trust what the facts have to say about the matter. And what they say is that the American League is the superior league.
Allow me to expound.
Head-to-Head: American League Is the Master of Interleague
The American League and National League don't have a Thunderdome to go to, but they do have the All-Star Game, the World Series and interleague play.
The National League has owned the first two in recent years, winning the last three All-Star Games and World Series. In the process, the Senior Circuit has proved...uh, well, not much.
Nobody actually thinks the All-Star Game is a definitive proving ground, right? It's a mere exhibition at heart, and the rosters aren't guaranteed to pit the AL's best against the NL's best so long as the fans are voting for starters. Also, managers have to worry just as much about getting their players in the game as they do about actually winning it.
As for the Fall Classic, it shouldn't be viewed as an event that crowns the best league. It's meant to crown the best team, and some will argue that it doesn't even do that effectively.
That leaves interleague play as the best proving ground. All AL and all NL teams participate in it, and interleague play leaves us with a big enough sample of games every year to draw a definitive conclusion about which league is better.
And for a long time now, it hasn't been close. Ever since 2004, the American League has ruled the interleague domain.
Here's a look at the records and run differentials for each league in interleague play since it began in 1997:
*Statistics are courtesy of Baseball-Reference.com and are current as of the start of play on Monday, May 28.
The AL has been getting the better of the NL for nearly a decade now, and you can see by the run differentials that it hasn't been particularly close. Even as the National League has taken control of the All-Star Game and the World Series, the American League has still been the better overall league.
Interleague play is a regular thing for the first time in 2013 now that the two leagues each have 15 teams, but the American League is maintaining its edge even though its newest club was the worst in the National League last year. The Houston Astros have done their part, too, winning two of their first four interleague contests.
The explanation for the American League's dominance? Those run differentials make it look like the AL's edge is an offensive one, but give NL hitters some credit. They're hardly out of their league next to American League hitters.
Offense: AL Lineups Are Deeper, But NL Hitters Are No Joke
Because of the DH, it's a fact of life that American League clubs are always going to have deeper lineups capable of scoring more runs. This has been true in the interleague era, as AL clubs have averaged 4.83 runs per game from 1997 until now. Compare that to 4.54 for NL clubs.
However, you may be surprised to hear that American League hitters haven't traditionally been demonstrably better than National League hitters in the interleague era.
Here's where we turn to Weighted On-Base Average, or "wOBA" for short. It's a stat that's a favorite of FanGraphs and similar to OPS in that it attempts to measure a hitter's overall quality. Where it differs from OPS is that it weighs different offensive outcomes in proportion to their run values, making it slightly more accurate than OPS.
Courtesy of FanGraphs, here's a look at the progression of the average wOBA for each league's non-pitchers (i.e. all position players) in the interleague era:
Strip away the pitchers, and the National League had more productive hitters than the American League for a while. It's only recently that things have leveled out, and things have really leveled out.
Since the start of 2010, the average wOBA for an AL non-pitcher is .322, compared to .321 for an average NL non-pitcher. The American League has been home to better hitters over the last three-plus seasons, but the difference is minuscule.
There's no getting around the fact that AL clubs have deeper lineups thanks to the DH, but the National League's own hitters are far from a joke next to American League hitters. As such, there must be some other explanation for the length and degree of American League dominance since 2004, right?
There certainly is. The truth is that the American League's edge is more on the mound than it is at the plate.
Pitching: AL Pitchers Are More Battle-Tested
Sort of like how American League clubs are always going to be better run-scoring teams because of the DH, National League clubs are always going to have better pitching numbers because of how pitchers have to bat for themselves.
The National League's ERA since the start of the 1997 season averages out to 4.23. That's compared to 4.46 for the American League. It's been the same old story since pitching started to rise to power in 2010—the average NL ERA since then is 3.90, while the AL's is 4.13.
Yet here's the funny part. When American League and National League teams have hooked up since 1997, it's traditionally been American League clubs that have had the pitching edge. Often in a big way, too.
Here's a look at the interleague ERAs for each league from 1997 to now, courtesy of Baseball-Reference.com:
| Year | AL Inter. ERA | NL Inter. ERA |
|---|---|---|
| 1997 | 4.23 | 4.32 |
| 1998 | 4.45 | 4.32 |
| 1999 | 4.97 | 4.54 |
| 2000 | 4.55 | 4.72 |
| 2001 | 4.30 | 4.30 |
| 2002 | 4.09 | 4.15 |
| 2003 | 4.67 | 4.59 |
| 2004 | 4.38 | 4.59 |
| 2005 | 3.91 | 4.61 |
| 2006 | 4.11 | 5.05 |
| 2007 | 4.38 | 5.05 |
| 2008 | 3.70 | 4.57 |
| 2009 | 3.91 | 4.46 |
| 2010 | 4.16 | 4.37 |
| 2011 | 3.59 | 4.01 |
| 2012 | 3.79 | 4.25 |
| 2013 | 3.82 | 4.30 |
The National League's typically superior pitching has been inferior in interleague play, while the American League's typically inferior pitching has feasted. There's been a particularly big divide since the start of 2010, as the AL's ERA in interleague play averages out to 3.84, while the NL's averages out to 4.23.
It helps that the American League is home to some of the best aces in baseball these days. Seven of the top 10 pitchers in baseball in terms of FanGraphs WAR since the start of last season call the American League home. That includes four of the top five.
But beyond that lies another reality: Strip away their performances against opposing pitchers, and National League pitchers are really nothing special.
This chart compares the performances of American and National League pitchers against non-pitchers, as measured by opponent OPS and strikeout-to-walk ratio. The numbers are from Baseball-Reference.com, and green signifies where the edge lies.
These aren't numbers for interleague games. These are numbers for all games, and they show that AL pitchers have tended to perform better against, you know, actual hitters than their NL counterparts. The NL has the advantage so far this year, but there's still a ton of time for that to change.
Here's where the American League's dominance of interleague play since 2004 really makes sense. The National League has some darn fine hitters, but its lineups aren't as deep as the American League's and, by extension, its pitchers aren't as battle-tested as American League pitchers.
These advantages haven't shown through in the All-Star Game or the World Series the last few years, but it certainly matters that they've shown through in the large sample size of interleague play.
The Wrap-Up
The National League gets points for winning the last three All-Star Games and for providing the World Series winner in each of the last three years. Without these feathers in the Senior Circuit's cap, we're probably not even bothering to have this discussion.
All the same, what it comes down to is that the American League's domination of the National League in interleague play since 2004 is no fluke. Despite what the All-Star Game and the World Series have to say about the matter, the AL is still the deeper and better league.
We've looked into the on-the-field explanations, which are simple. Though the NL has some fine hitters, the AL has a natural offensive edge, and that edge has helped breed battle-hardened pitchers.
As for the off-the-field explanations, it helps that there's plenty of money to be found in the American League. According to the Associated Press, seven of the top 10 spending teams in baseball this year are American League clubs. In terms of revenue, the New York Yankees and Boston Red Sox are regulars at the top of Forbes' revenue charts.
Those two clubs just so happen to be responsible for many of the American League's wins in interleague play. The Yankees are 174-115 in interleague, and the Red Sox are 162-122.
However, low-revenue AL clubs have also contributed. The Oakland A's are 155-130 in interleague play. The Tampa Bay Rays were an interleague doormat for many years, but they've been better ever since 2008. In lieu of money, what these two teams have are great front offices.
A different narrative exists in the National League. The huge-market Los Angeles Dodgers are 117-141 in interleague play. The small-market Pittsburgh Pirates are 94-141 in interleague play. On one side, a rich franchise that has let a lot of money go to waste. On the other, a poor franchise that hasn't found ways to overcome its limits.
So call it a combination of different things that are responsible for AL superiority. American League rosters are capable of winning any battle, and the American League is where you can find great and small amounts of money being put to good use.
The pendulum will swing back towards the National League someday. It might not happen until the NL gets the DH and the playing field is leveled, but it will happen eventually. The American League bubble won't be able to avoid bursting forever.
But for now, it's holding strong.
Note: Stats courtesy of Baseball-Reference.com unless otherwise noted.
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