Playoff Prospectus: Na... (10/05)
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October 6, 2012 BP UnfilteredPlayoffs and Home-Field AdvantageSince 1995, home teams have won 53.936 percent of baseball games played in the regular season. Considering that a large portion of home field advantage is, by conventional wisdom, attributed to the effects of home-crowd fans (either on the players, or, more likely, on the umpires), we might reasonably expect the home team to get an even bigger boost during October, when the crowds are bigger, perhaps more partisan, and generally more bananas. Since 1995, home teams have won 53.986 percent of baseball games played in the postseason. This number is somewhat less reliable because the sample size (552 games) is so much smaller, but if it we conceded it is an accurate representation of the postseason home-field advantage, it would mean that the home teams in the past 18 years of playoffs have won a total of 0.27 more games than they would have won in a regular-season environment. Which is to say, zero games. So, identical. Surprising and interesting, is all. (Update: Complicating this is also the fact that "better" teams would probably get to play a few extra home games in October, because of how the playoff rules work. So by a small amount, the home team should be, on average, a bit better than the visiting team in October; in the regular season, the teams are, on average, equal.)
Sam Miller is an author of Baseball Prospectus. Follow @SamMillerBB
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Have to say, I would have to think the home-team advantage is way more attributable to getting last ups, as opposed to any crowd factor. It's a big advantage late in the game, and even more so in extra innings, to be able to end the game in your at-bat but always to be able to match any visiting-teams runs. Apart from the better team getting home-field advantage.
I agree. A visiting team needs to win a game in 9 innings, a home team has to win it in 8.5 innings. Also a 0.27 edge is still pretty significant, especially if a team that goes to the World Series would play anywhere from 10 to 19 games.
Sam says that the home team has won .27 more games, NOT per series, NOR per season, but rather out of 552 games over an 18 year period.
If my stubby little fingers pushed the right buttons on the calculator, that 53.986 post season winning percentage comes out to a record of 298-254.
A 59.936 regular season winning percentage would result in a record of 297.73-253.27.
As a team can't actually win .73 games, it rounds up, and comes out perfectly as predicted by the regular season winning percentage.
That is what is commonly known as a rounding error. It is not "still pretty significant" at all.
I did use the 0.27 wrong so thank you for correcting me.
I think part of what Sam is also saying is that the home field advantage during the playoffs specifically should be amplified when it is not. In general, though, he seems to suggest a home field advantage exists in general. It just doesn't get much of a playoff bump.
The mechanical advantage of the ordering (visitors bat first) is unclear. It influences player substitution, but each side gets an advantage:
1) The visitor can choose pitchers and defenders based on the score. With a one-run lead, they can put in their best pitcher/defense and aggressively substitute based on match-ups. With a tie, they can more strongly consider the impact on future innings.
2) If the visiting team took a lead in the top half, the home team can aggressively use bench players to pinch hit or run, because they know they have to score or lose. If its tied, they know they have to think about additional innings.
Short version: Does 'bats last' necessarily overcome 'pitches/defends last'? What percentage of extra-inning games are won by the home team? Bigger or smaller than the 54% generic home-field advantage?