Home Field Advantage in MLS (and Goals Scored Home vs Away)

EDIT 7/17/08: Edited to include full 2007 stats. In the nearly 2,000 MLS games over the past 11.5 seasons, playing at home has certainly been important (like in any sport). But just how important has it been? That's what I've attempted to find out, and in this update of a similar post from last year, I'll provide the numbers. This is not an examination of what causes home field advantage, but rather exactly what that advantage has resulted in on the field. Throughout MLS history, the average PPG by every team in every game is 1.385. That's the basic equivalent of a .500 team (I find that it's much easier to use PPG rather than winning percentages in soccer). Actually, it's probably a little less due to the lower number of draws in the early years and also thanks to overtime from 2000-3. It's about 1.36 over the last four years. So that's average of every team in every game, 1.385. That means there's an average of 2.77 points taken from any one game, which is less than 3.00 because of draws. The table below breaks that down into home points vs away points, and then the final column on the right is the difference between the two, aka home field advantage. The all time home field advantage in MLS is 0.67 PPG. In other words, that translates to 20 points over a 30 game season. In general, the HFA seems to have been higher in seasons with more parity, which is understandable. Just look at how it dipped in 2005, when there were two absolutely awful teams and two really good ones. I guess I'll need to figure out the variance (or whatever) for each season and compare it to HFA in the future. Performance of Home Teams in MLS Year Games W L D Home Away Diff 1996 160 84 42 34 1.79 1.00 0.79 1997 160 81 46 33 1.73 1.07 0.66 1998 192 101 58 33 1.75 1.08 0.67 1999 192 80 55 57 1.55 1.16 0.39 2000 192 105 53 34 1.82 1.01 0.81 2001 158 83 47 28 1.75 1.07 0.68 2002 140 77 41 22 1.81 1.04 0.77 2003 150 71 38 41 1.69 1.03 0.66 2004 150 72 32 46 1.75 0.95 0.80 2005 192 92 56 44 1.67 1.10 0.56 2006 192 92 44 56 1.73 0.98 0.75 2007 195 91 54 50 1.66 1.09 0.57 Total 2073 1029 566 478 1.72 1.05 0.67 If you want to look at it another way, home teams get 62.2% of the points. I suppose that this actually a better way to look at home field advantage, since it takes out the affect that the number of draws has on PPG. To clarify, what I mean is that the total number of PPG will be different each year (i.e. 2.75 this year, 2.71 last year). Home Point Percentage Year Home PCT 1996 64.1% 1997 61.7% 1998 61.9% 1999 57.2% 2000 64.4% 2001 62.1% 2002 63.6% 2003 62.1% 2004 64.9% 2005 60.2% 2006 63.8% 2007 60.4% Total 62.1% I've gone a little further this year and taken a look at exactly how many goals are scored both home and away. On average throughout league history, the home/away breakdown is 1.75 vs 1.28, for a 0.46 goals per game difference. Goals Scored by Home Teams vs Away Teams Games Gol GPG HG AG HGPG AGPG Diff 1996 160 539 3.37 321 218 2.01 1.36 0.64 1997 160 522 3.26 302 220 1.89 1.38 0.51 1998 192 685 3.57 391 294 2.04 1.53 0.51 1999 192 549 2.86 305 244 1.59 1.27 0.32 2000 192 612 3.19 351 261 1.83 1.36 0.47 2001 158 519 3.28 297 222 1.88 1.41 0.47 2002 140 421 3.01 246 175 1.76 1.25 0.51 2003 150 433 2.89 248 185 1.65 1.23 0.42 2004 150 392 2.61 234 158 1.56 1.05 0.51 2005 192 551 2.87 306 245 1.59 1.28 0.32 2006 192 503 2.62 293 210 1.53 1.09 0.43 2007 195 518 2.66 297 221 1.52 1.13 0.39 Total 2073 6244 3.01 3591 2653 1.73 1.28 0.45 Let's break this down into percentages too. So basically, a very small change in the percentage of goals from year to year. Not too shocking when you consider this is over anywhere from 140 to 192 games. Home Goal Percentage Year Home PCT 1996 59.6% 1997 57.9% 1998 57.1% 1999 55.6% 2000 57.4% 2001 57.2% 2002 58.4% 2003 57.3% 2004 59.7% 2005 55.5% 2006 58.3% 2007 57.3% Total 57.5% One last thing, I want to see how the the home point percentages compare to the home goal percentages. Can we gather anything from that? The two are obviously related, but this appears to show that given the percentage of home goals this season, home teams should really be doing better. Maybe that's due to the number of blowouts? There have been 11 home wins of 3+ goals in 2007, versus only one away win of 3+ goals. A quick check, and I believe last year it was 15/5 (home/away). Home Point Percentage vs Home Goal Percentage Year Pts PCT Gol PCT Diff 1996 64.1% 59.6% 4.6% 1997 61.7% 57.9% 3.9% 1998 61.9% 57.1% 4.8% 1999 57.2% 55.6% 1.7% 2000 64.4% 57.4% 7.0% 2001 62.1% 57.2% 4.9% 2002 63.6% 58.4% 5.1% 2003 62.1% 57.3% 4.8% 2004 64.9% 59.7% 5.2% 2005 60.2% 55.5% 4.6% 2006 63.8% 58.3% 5.6% 2007 60.4% 57.3% 3.0% Total 62.1% 57.5% 4.6% For comparison purposes, last year in the Premiership in England, the home/away difference was 0.65 PPG. Home teams won 61.8% of total points. The home/away goal difference was 0.46 per game. Home teams scored 59.3% of total goals. Further reading: http://www.treatmentonline.com/treatments.php?id=1277 http://www.metrofan.com/forum/showthread.php?t=381837 http://www.bigsoccer.com/forum/archive/index.php/t-106332.html http://www.hiremetheo.com/internal/thesis.pdf http://sabermetricresearch.blogspot.com/2007/03/home-field-advantage-and-testosterone.html