03 October 2015

The Myth of Home Field Advantage

The Mets and Dodgers are engaged in a great battle, testing whether their team, or the other team, so dedicated to the proposition of winning the World Series, can long endure. They are met on separate battlefields -- the Mets at Citi Field against Washington and the Dodgers in L.A. versus the Padres. 

A portion of that home field will serve as a final resting place for one team's playoff hopes so that the other team's might live on. 

Is it altogether fitting and proper that they should do this? 

Likewise, the Pirates and Cubs do indirect battle for home field in their one-game play-in. Will people little note, nor long remember, who batted last?

The answer, as even a Phillies fan in Gettysburg can see, is that these are very different questions.

For the season, home teams have emerged victorious roughly 55% of the time. Home cooking, familiarity with the field, a partisan crowd and the final at bat conspire to roughly a 10% advantage. That's not an insignificant edge in a game pitting essentially even teams like Pittsburgh and Chicago in a single, sudden-death tilt.

New York and L.A. are also essentially even, having both played .560 ball this year en route to division titles. But home field conveys so much less advantage to them, even though the Dodgers have won two-thirds of their games at Chavez Ravine and just 45% of their games as the visitor. 

Their series will be five games long. The home team enjoys an advantage if the series goes three or five games. The margin of that edge can be expressed this way: in a 21-game series, the home team can be expected to win 11 times. Not really a game-changer.

In a seven-game playoff, it's so much less significant. In series that end after four or six games, each team will have hosted half the contests. In a five-game set, the lower-ranked team actually has the home field advantage in a 2-3-2 format. 

So home field "advantage" is a small disadvantage in a truncated seven-game series and is a benefit only in the full seven, and even then, worth just 10% in that one game. Because roughly a quarter of series extend to their full measure, homefield accounts for just a 2.5% edge. That's the difference between the Mets at 89-70 and the Dodgers at 90-70, which is where they stand at this writing. Factoring in the home field deficit through Game Five, the total value of the better record is essentially a rounding error.

You'd rather have home field than not, but teams would be much better advised to spend their time arranging their rotations, resting their bullpens, healing the injured and preparing their entire rosters psychologically for the amped emotions of playoff baseball. 

And "analysts" would be better advised to just shut up about home field advantage.

2 comments:

Anonymous said...

What about Royals-Toronto? They're vying for best record in AL.

Waldo said...

Good question. I side-stepped that situation because it's different. The winner of that sweepstakes will not only get seventh games at home, they will play the Wild Card winner in the first round. Theoretically, that means a lesser opponent that had to burn up its ace in the play-in game, although in practice that hasn't proved to be much of a benefit.