Wired.com: So why does the home team win more often?
Wertheim: What’s really interesting is how consistent that truism is. The WNBA has almost the exact same home winning percentage as the NBA. A soccer league in Central America is almost the same as the Premier League. Japanese baseball has almost the same as MLB.
Before you even dig into the “why?” of home-field advantage, you see the data that 100 years ago the home winning percentage in Major League Baseball was almost exactly the same as it is today, and you find the same in other sports.
I think most people think, “Well, you’re playing at home and you’ve got people cheering for you and booing the other the guy,” but we didn’t find that to be the cause. Then you have the theory that home teams get to sleep in their own beds and road teams had to fly in the night before, but that didn’t seem to be the case either.
Wired: Right. You made the point in the book that travel has gotten so much better than 100 years ago, but winning percentage didn’t change from when teams were on buses to now, when they’re taking charters.
Wertheim: Yeah, and in games like when the Angels play the Dodgers or the Ravens play the Redskins — games where there’s negligible travel — the winning percentage stays the same. If you fly across the country, you’re not losing any more than you are when you’re the Chicago White Sox playing across town at Wrigley Field.
So we looked at how games are called and that’s where the data went berserk. Yellow and red cards in soccer, calls in the NFL before and after replay’s implementation, called balls and strikes in baseball — that’s where we saw games are called totally differently based on where they’re played. And the more attended the games are, the more striking the bias.
I'm looking forward to seeing the book (soon, I think) and the data. But this does reinforce something that's been floating around in my head for a long time (because I read it somewhere): Most (if not all) of the home-field advantage is the result of the officials subconsciously wanting to avoid getting yelled at by the fans. And it wouldn't take much to cause a measurable effect. There are how many pitches in the average baseball game? Something like 300? And how many of those could reasonably be called a ball or a strike?
It doesn't take many of those going one way to show up in the hitting and pitching stats, and to change the outcome of the game.
Like I said, I still want to see the numbers. And it's not like nobody's ever studied this stuff before. But there's nothing wrong with standing on the shoulders of the giants who have come before, plus there's always more data available. I would love to find a littlte place in my head for this home-field thing, and have room for other stuff.