Monday, December 3, 2012

A Richly-Deserved Beating: CFB ATS Update

At the beginning of the college football season, I asked whether you could use a team's recent against-the-spread (ATS) history to predict how they would do against the spread this season. I came to the conclusion that
[T]he perpetually underperforming teams (like Tulane) and perpetually overperforming teams (like Boise State) are a function of luck* rather than some underlying market inefficiency.

Well, the season's over (except for the bowl games). Was I right?

I think so. Let's start by looking at the top six teams ATS from 2003-2011, and see how they fared in 2012. (Just like last time, these numbers are from
Cover %
Best Teams ATS'03-'112012
Ohio State61.658.3
Utah 59.841.7
Boise State58.250.0

Clearly, this is a mixed bag at best and a losing proposition at worst. Betting $100 on these teams for every game they played would have resulted in a $700 loss.

How about our lovable losers? Are they still flying under the radar?
Cover %
Worst Teams ATS'03-'112012
Fla Atlantic41.666.7
Miss State42.450.0

Nothing mixed about this: each of these squads finished .500 or better against the spread. Bet $100 per game against each of these teams every week and you would have lost nearly $1,400 this season*.

* - Now granted, I'm deliberately overlooking the games like Memphis-Tulane and Oregon-Utah where you'd be betting on both sides of the same game. But there are so few of those games that they're basically negligible.

It just goes to show you have to be careful when coming up with gambling rules. Pick something too obscure ("the Green Wave are 5-0 ATS when coming off a night road game in North Carolina that they lost by 10 or more") and you end up putting too much faith in a microscopically small sample size. Pick something too obvious -- like this -- and the people who look at this stuff for a living are probably aware of it as well.

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