All three home teams won their MLS games on Sunday. Not a big deal, right? Well, it at least starts to look like one if you see it as part of a larger trend going back about three weeks. Since the weekend of Aug. 10, home teams have gone an astounding 21-3-6. Put another way, they've won 70 percent of their games.
And it's not like the schedule just hit a weird patch where very good teams were playing at home. Among the more notable results are Chivas USA beating the Supporters' Shield-contending New York Red Bulls 3-2; the New England Revolution crushing the Philadelphia Union 5-1; and the Montreal Impact dismantling the Houston Dynamo to the tune of 5-0. And those were just games from this past weekend.
Is this the heralding of a new MLS era in which home teams are near locks? Probably not.
As astounding as this recent spate of results may be, the season as a whole looks pretty similar to what you'd expect from around the world. Teams are roughly .59 goals better at home than they are on the road. The general rule of thumb around the world is that home teams are about .5 goals better at home. I'd say a .08 goals is notable, but probably not something worth covering for your statistical thesis.
What is a little more interesting, at least from this perspective, is that this goal-difference is a bit of a change from years past. I only went back to 2010 for this study, but you can see a changing trend. Last year, teams were about .49 goals per game better at home than on the road. In the two years before that, it was closer to .42 and .40, respectively. Those are probably the kinds of numbers you'd associate more closely with a league driven entirely by parity, which MLS has been and will be for the foreseeable future.
But the growing gap, at least to me, suggests that there is a growing divide, at least in subtle ways. In a league where results are determined virtually by coin-flip, you wouldn't expect there to be a huge gap between home and away splits. Over the last four years, at least, we have seen that gap grow.
What will be interesting is if the current three-week trend continues for much longer. The way the MLS Cup playoff are structured, home-field advantage is not really that big of a deal, at least until the finals. But now that the finals are being hosted by the team with the best record, there's a lot more value in home-field advantage than there once was.
Before we get too far ahead of ourselves, though, it's worth noting that while the goal-difference suggests some significant change, the winning percentages do not. Sure, this year we have just one team that doesn't have a losing road record and that team, Sporting Kansas City, is barely 5-5-3, but the actual winning percentages of home and road teams are basically the same as last season. Home teams have won 51 percent of games this year, while road teams have won 23 percent. Last year, those numbers were 52 and 24. In 2011, as you may remember, there were a lot of ties, so the winning percentages were 43 and 22. In 2010, for the record, it was 49 and 28.
Ignoring what seems to be the actual outlier of 2011, it doesn't look like things have changed all that dramatically, especially if you consider that the last couple weeks have been pretty extreme. I think we can safely say that MLS has become a league were the home team wins about 50 percent of the time and the road team pulls out three points somewhere around 25 percent. I'm not sure that's very earth-shattering, but that's where we are.