American League Dominance?

The All Star break is a great time to take stock, and we have heard from the pundits. Major League Baseball’s American League is so much better than its National League that many pundits would cancel this year’s World Series and crown the ALCS winner the MLB champ. So, let’s take a look at some data to see if they are on the right track.

The American League won 154 interleague games this year and lost only 98. That is a remarkable fifty-six games over 0.500. So, the AL has won 61% of the games in 2006, and conversely, the NL has only won 39% of the time. This was the worst performance by any league since interleague play began ten years ago (see table). In fact, the worst beating of one league by the other prior to this year was the NL’s dominance of the AL in 2003 when the NL won 137 games to the AL’s 115.

Out of ten seasons of interleague play, the AL has accumulated four seasons when it finished more than ten games over 0.500 (including one season when it finished 12 games over 0.500, the closest margin in this analysis), and the NL has accumulated three such seasons. Three times the leagues finished within ten wins of each other. If we expand the criteria that determine superiority to fifteen games over 0.500, we find that the AL earned that in three seasons, the NL in three seasons, and they finish within fifteen games of each other in four seasons. These numbers fail to show the dominance of one league over the other.

Overall, the AL’s superior record in 2006 eliminated the deficit it had accumulated in the nine prior seasons. Prior to 2006, the AL had won 1,095 times to the NL’s 1,104, which is a record that statisticians would show is not different from 0.500—again, no dominance here.

YEAR AL NL
1997 97 117
1998 114 110
1999 116 135
2000 136 115
2001 132 120
2002 123 129
2003 115 137
2004 126 125
2005 136 116
2006 154 98
Totals 1249 1202



If the prior nine years show a virtually identical winning percentage for the two leagues, and each league had the same number of superior seasons, what is different about this year? What is influencing the pundits to believe that there has been a major shift in superiority? Has there been a major shift in talent from the NL to the AL, or is something else at work here?

One thing that might be influencing popular opinion is more recent history. Last year the AL won 136 games, making their two-year record 290 wins and 214 losses. The last 0.500 season was 2004 and the NL's last winning season was 2003. Another might be the AL’s recent dominance in All-Star games. The AL is 8-0-1 in the last nine years. Another might be the AL sweeps of the NL in the last two World Series. The NL hasn’t won a World Series game since Florida won game six in 2003 and took the series from the Yankees 4 - 2.

Still, statisticians would be hard pressed to make a case of AL dominance on only two years of data, or even nine years of All Star results when the best pitchers rarely pitch in the game. And, the NL did win two of the last five World Series, which is not statistically different from 0.500.

What Do We Remember?
Ultimately, the main thing that people remember about any particular baseball season ten years later is who won the World Series in that year; we really only care about championships. Does anyone remember which league was better when the Big Red Machine was crushing the AL in the 70s, or when the A’s took three straight championships? Probably not. We don’t really care which league is better on average or which league has better all stars on average.

So, does a winning interleague or All Star record give us any clues of the eventual World Series winner? There aren’t many observations, so this argument will be built mostly anecdotally, but at least it is an attempt to be objective, unlike the hysteria that followed interleague play this year.

First, let’s examine the record in All Star play since the respective leagues were broken into divisions in 1969. In that time, MLB held thirty-six World Series and the AL has won twenty-one of them. In the last ten, the AL has won seven. But, does the league that wins the All Star game also win the World Series?

Since and including 1969, there have been thirty-five seasons in which the All Star game did not result in a tie and in which a World Series was played (in 1994 they played an All Star game that was won by the NL, but the World Series was cancelled due to the players strike; in 2002 the All Star game resulted in a tie). In those thirty-five years, the winning All Star league correctly predicted the league that produced the World Series winner eighteen times; so, the All Star game incorrectly predicted the World Series winner seventeen times. Don’t bet the ranch on the World Series based on the All Star game.

What about interleague play? Well, we only have nine years of interleague play where we know the World Series winner, which is not a lot to go by. In those nine years, the AL was more than fifteen games over 0.500 twice, the NL three times, and they were within 15 games of each other four times. So, in five seasons of “conclusive” interleague play, the “convincing” interleague winner correctly determined the league that won the World Series four times. But, are five observations enough to get you to bet the ranch?

Even an eighty-percent accuracy rate is not enough to convince me in only five seasons of results. Looking at the All Star results again, there were two stretches of five years when the winning All Star league could not predict the World Series winner (1970 through 1974 and 1984 through 1988). I would wait for more results.

Interleague Play
While ten years from now we will probably only remember who won the 2006 World Series and not much more, I still want to know what led to this year’s interleague results. Is the AL that much better than the NL on average?

This year the NL East, Central, and West played the AL East, Central, and West, respectively, in interleague series. Here is one statistic that I found compelling: While the entire AL was fifty-six games over 0.500, just four AL teams were a combined fifty games over 0.500 against the NL, and three of those four played in the American League Central. Hmmm. The devil is in the details. So, the other ten AL teams are simply 0.500 teams when playing the NL, which is closer to what I’d expect.

The four dominators are made up of the Red Sox, Tigers, White Sox, and Twins. The Red Sox are an interesting team. They are certainly very good and lead the AL East by three games over the Yankees. But, the Red Sox are especially good at home where they are 27-10 this year. They are merely 26-23 on the road.

The Red Sox played against the NL East this year and as luck would have it, they played six of their toughest nine interleague games at Fenway. They played a home and away series against the second-place Phillies, and they played all of their games against the first-place Mets at Fenway. Details.

At the time that the Mets played the Red Sox, the Mets had a twelve-game lead in their division and had several players who were nursing injuries. The best thing about running away with a division is it gives a team time to rest its players, especially the injured ones as the Mets did in the Red Sox series with Wright, Floyd, Nady, and Delgado. Details.

One could argue that the Red Sox home-field advantage is exaggerated against NL teams that are not used to playing in such a ridiculous, albeit historic, ballpark. The Sox are 11 – 1 against NL teams at home in the last two years. Interestingly, the NL team with the best record in interleague play this year is the Colorado Rockies, which also plays in a ridiculous place.

Amazingly, the combined home record of the four AL juggernauts is 116 - 48 for an absurd 0.707 winning percentage. But in a World Series, these teams will also have to play games on the road where they are a combined 100 – 84, or 0.543, which is still very good, but not dominating. More than likely one of these teams will face the Mets in the World Series. The Mets are 27 – 18 at home and 26 – 18 on the road.

How about the other three AL juggernauts? Each came from the AL Central. Is anyone surprised that the AL Central dominated the NL Central this year? The NL Central is the only division in baseball that has two sub-0.400 teams. The Chicago Cubs and Pittsburgh Pirates have to be the two worst teams in baseball. It is simply luck that the two best teams in baseball play in the AL Central this year and that they got to play the two worst teams in baseball in interleague play.

On average, the AL might be better than the NL this year, but it is impossible to conclude that the AL is significantly better than the NL. And, the NL might still have the best team. One has to pay attention to the details.