The first thoughts in this direction came after Saturday night's game, where a crowd of over 37,600 cheered on Barry Enright and the Diamondbacks at Chase, to a 3-1 victory over Ubaldo Jimenez and the Rockies. It reminded me of SnakePitFest v3.2, where a full house enjoyed a walk-off home-run by Chris Young, after which he said, "When you're out there in the field and you hear the screaming fans it definitely makes a difference for us. Pretty much the fans got us the win tonight." Is that the case? Do home teams in general - and Arizona in particular - play better when there are more people in the stands?
After the jump, we'll take a look to see if there's evidence for this.
More analysis is clearly needed. Next step: average attendance at Chase Field this year for losses: 24,661. For wins: 25,888. That suggests a slight tendency for the team to play better in front of more people. However, if you try to correlate runs scored and runs allowed against crowd numbers, you get the complete opposite result. Runs scored has a marginally negative correlation of -0.06 and runs allowed is fractionally positive (+0.09). That means, the Diamondbacks score less and allows more as the crowd goes up, though it's a pretty weak connection.
One of the things to note is that not all large crowds are created equal. When Luis Gonzalez retired, just about everyone in the park was cheering for the Diamondbacks. On the other hand, while the number in attendance for the game against the Yankees was almost the same, the crowd was much more evenly-split, and any fan-related energy would seem to apply in the appropriate proportion. It also is likely the case that good teams are more likely to draw fans to Chase: while the Diamondbacks may play better, they could well also be facing better opposition. Again, the Yankees provide a good example of this.
But let's expand things: given the somewhat... "relaxed," shall we say, nature of the Phoenix fan, might we find more impact elsewhere, in cities better known for a rabid fanbase? As a measure of increased home performance, we take the winning percentage of a team there and subtract the winning percentage on the road. The difference which results ranges from zero - Tampa Bay have the same record at Tropicana and elsewhere - to .303, for Detroit, who are 43-24 at home and 20-39 on the road. We then match that against the average crowd for that team. The theory would be, a big home crowd should result in an improved home/road differential. Is that what we see?
Here are the results for all thirty major-league teams, through Tuesday night's games:
|Tm||Hm W-L||W%||Rd W-L||W%||Diff||Att|
The correlation between differential and attendance is 0.140; present, but not huge. It seems to have more effect at the lower end of attendance. Of the bottom 13 teams in attendance, only three - the Pirates, Nationals and A's - have a differential more than ten points better than league average (.128); two are within ten points of it, and eight are 20+ points lower However, there are exceptions: the Yankees, Angels and Cubs are all well-attended, with differentials below average. I also correlated % of park capacity against the differential to see if it was better to have a small, full stadium, than a large, half-empty one. However, the correlation there was only 0.046, basically negligible.
Specifically with regard to the Diamondbacks, our home-road differential is marginally above average, despite the lackluster crowds at Chase this year. I thought I'd also crank the wayback machine up, and see what the numbers were for Arizona, for each year in franchise history. Did the crowds that packed the stadium in 1998, lured by the novelty of baseball, lead to an improved home-field advantage for the team? In two word: not much. Here's the same chart as above, done for each season of Diamondbacks history.
|Year||Hm W-L||W%||Rd W-L||W%||Diff||Att|
There's pretty much no discernible trend here either. The correlation over the history of the Diamondbacks is 0.173, in line with the overall MLB number this season. Again, the lowest attendances - 2005, 2006 and 2009 - tend to equate in general with the lowest differentials, but there are exceptions, such as this season, where Arizona are performing much better at home [this year's differential is the second-highest in franchise history]. As in the majors overall, while there seems to be a slight connection, you'd be hard pushed to claim much predictive effect.
There is certainly a benefit to playing on your own turf. Over the 1,215 games played last season, the home team won 54.9%, very close to the numbers in the two years prior to that (55.6% and 54.2%). That only works out to about four games over the course of the season, perhaps not as much as you might expect. From what we've seen here, the home crowd - or, at least, their basic number - do not seem to be a significant part of that benefit, probably representing only a fraction of a win in a year. Maybe the silent majority at Chase are right to save their energy!