To catch up, quickly: ESPN accused the Blue Jays of stealing signs in 2010 based on an anecdote from unnamed players on an unnamed team Among the evidence in the article is the fact that the Jays hit 150 HRs at home (but only 107 away). As far as the numbers go, you might think that's an extreme split. But fortunately, we have the capability to look up, online, home/away disparities and make comparisons. It's worth pointing out that nearly every team in the league hits better at home than away-the comfort of the ballpark, the familiarity with the batter's eye, and the luxury of being able to sleep in one's home bed has some amount of effect.
So how extreme was the Blue Jays' home park effect? Let's just look at wOBA and see which teams got the biggest boosts from hitting at home.
Toronto Home wOBA: .346 Away: .321
Colorado Home wOBA: .373 Away: .292
Yankees Home wOBA: .365 Away: .330
Boston Home wOBA: .351 Away: .339
Arizona Home wOBA: .343 Away: .306
Texas Home wOBA: .349 Away: .318
White Sox Home wOBA: .349 Away: .313
Atlanta Home wOBA: .338 Away: .316
I threw the Yankees and Red Sox in because they were mentioned in the ESPN article as two teams who've complained about the Blue Jays allegedly stealing signs in the past. I also included the Braves just for comparison's sake, since this a Braves' blog. The other teams are those which had fairly extreme looking splits. Interestingly, the White Sox are supposedly the anonymous team to which the particular anecdote is attributed-the basis of this story.
The Blue Jays were .025 points better at home than away. That's less than the Rockies, clearly, but also the Yankees (.035), Diamondbacks (.037), and White Sox (.036). Atlanta's difference of .022 was a bit greater than average as well.
Ah, but the article is specifically talking about the home run and power increases, and seems to point out that despite having a worse OBP, the Blue Jays were still able to hit a lot more home runs at home thanks to the sign stealing. So let's look specifically at Isolated power, which is just SLG-BA, and see how dramatic the power increase at home was.
Toronto Home ISO: .230 Away: .183
Colorado Home ISO: . 199 Away: .125
Yankees Home ISO: .193 Away: .147
Boston Home ISO: . 180 Away: .183
Arizona Home ISO: .185 Away: .148
White Sox Home ISO: .181 Away: .125
Atlanta Home ISO: .153 Away: .133
Again, New York and Boston were included because they've made these allegations in the past, and the Braves because this is an Atlanta blog. The others had extreme splits. The .047 ISO boost at home for the Blue Jays does seem extreme, but it is still less than the Rockies' boost for obvious reasons. It's also less than the .056 boost the White Sox got (again, the likely anonymous team making the allegations) and just .001 more than the .046 boost that the Yankees got at home.
Again, I wouldn't know if the Blue Jays were out there stealing signs, and the math alone certainly can't disprove this, but it does seem to disparage some of the "evidence" that ESPN is using to back up their story. Toronto hit a LOT of home runs last year at home. They also hit several on the road. They were a team that boasted several high power/low OBP guys, to interesting effect. They were the best home run hitting team at home, yes, but one of the best home run hitting teams on the road also. Keep in mind that I only looked at 2010. If I'd wanted to find some more extreme home/away splits, I'm sure they were there to find in other seasons.
Big, big problem for me-If ESPN thought this was a legitimate story, why haven't they interviewed Vernon Wells, Alex Gonzalez, Shaun Marcum, John Buck, or any OTHER former Blue Jays who might be able to comment on this? If this was going on, I could understand current Blue Jays reluctance to comment on it, but perhaps former players might feel like mentioning it, if only to make sure their current teams don't lose a competitive advantage. It's fairly weak reporting, and yet it's been on Sportscenter like it's actually news. It's a rumor that has been reported as news, seemingly.
EDIT: Commenters drew to my attention that I should be looking at the difference between how Toronto hit in their home park to how well other teams hit in own park, or at least relative to the home/away difference in other parks. I was too lazy to do EVERY team (maybe if someone else wants to, they can fill in where I left off), but I did take 15 teams. I mixed in teams who had extreme home/road splits, along with other good hitting teams and good pitching teams, since home pitching is necessarily factored in when you do this. First I'll use OPS, since I got this from Baseball-reference. This is what it appears to be-hitting numbers for home teams in their home parks, and then the away teams in the same parks.
Toronto Home OPS: .799 Away Team at Toronto: .730
Seattle Home OPS: .623 Away Team at Seattle: .663
Texas Home OPS: .800 Away Team at Texas: .704
Milwaukee Home OPS: .766 Away Team at Milwaukee: .767
White Sox Home OPS: .796 Away Team at White Sox: .736
Boston Home OPS: .804 Away Team at Boston: .727
Arizona Home OPS: .787 Away Team at Arizona: .767
Yankees Home OPS: .832 Away Team at Yankees: .734
Colorado Home OPS: .866 Away Team at Colorado: .737
Atlanta Home OPS: .771 Away Team at Atlanta: .658
Minnesota Home OPS: .776 Away Team at Minnesota: .709
Tampa Bay Home OPS: .726 Away Team at Tampa Bay: .685
Philadelphia Home OPS: .765 Away Team at Philadelphia: .697
San Diego Home OPS: .678 Away Team at San Diego: .639
San Francisco Home OPS: .745 Away Team at San Francisco: .651
Wow, that home cooking for the Braves! A .113 difference at home. They hit very well at home, and the competition apparently did not. Clearly, good pitching and good offensive teams will have an advantage in this regard. The Rockies win this with the .129 difference, giving them a very strong home field advantage, while the Giants and Rangers also enjoyed home advantages near worth near 100 points of OPS. The Blue Jays .069 advantage appears fairly middling.
What happens, though, when we look at ISO? Let me keep this simple and give you difference between the home team's ISO and that of the visitors in each park.
White Sox: .035
Tampa Bay: -.005
San Diego: -.005
San Francisco: .030
Well, that actually surprised me. Without taking the time to run the numbers, that actually does appear to be over a standard deviation or two outside the mean. So what are we supposed to make of this? I'm not sure. It's worth noting that while the Blue Jays had the highest home ISO, and hit the most home runs of all home teams, they still hit the second most home runs, with the second highest ISO, of road teams. They were a powerful team last year. Did that get an artificial boost? I really don't think so, honestly. Things like these happen, and having the best home run hitting can lead you to having huge difference in ISO relative to opponents visiting your park. Clearly, more work needs to be done here. It's late, perhaps I'll revisit this tomorrow.