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Friday, August 30, 2013

Road Trip Recovery

On September 20, 2008, #2 ranked Georgia beat Arizona State in Tempe, 27-10.  A week later, they came out flat at home against Alabama and lost 41-30.  Nick Saban's Tide was on its way to an undefeated regular season, but it still served as a crushing loss for Georgia, who was favored by 6 points in the game.  Georgia fans bandied about many excuses for the loss, some valid, (injuries early, Bama having a superior game plan, etc) and some not (uniform color), but in some circles, an unusual excuse was made: some fans blamed the trip to Tempe.

The idea was that a road trip multiple time zones away was too hard to get home and recover from.  Never mind that in 2010, Georgia took a similar trip to Boulder and came home to whip rival Tennessee 41-14.  The narrative of the 2008 Tempe trip causing the loss to Alabama did hold with some Georgia fans.  I don't presume Georgia fans are unique in this regard; it's just the first time I personally heard about this theory.  However, unlike many theories, this one seemed testable, so here we go.

The process:  I took every current BCS conference team (plus Notre Dame), and their schedules since 1992 (the beginning of the expansion age).  Only looking at home games immediately preceded by road trips multiple time zones away, I looked at how they performed against the spread (games without spreads were omitted).  The spread seemed the only logical way to go.  This way teams aren't unfairly rewarded or punished for their scheduling.

The results:  The sample size consisted of 215 games.  The average team was a home favorite by 11.69 points.  They beat the spread by 1.76 points per game.  It's not a surprise that the result was close to the spread.  It is a surprise that the number was positive.  Not only did the long road trips not significantly hurt team's performances against the spread when they came home, but teams actually tended to be better than the spread.  I did consider the idea that some teams are better against the spread than others.  To account for this, I looked at how these teams did against the spread in their other games to find an "expected ATS", and I compared these games to that number.  They still beat their ATS averages by 1.63 ppg.

"But wait - some teams take weeks off, right?" Yes, and those were included in the numbers you see above.  Separating them, however, doesn't change the outcome too much, though the week off certainly does help:

  • With no week off: +1.66 ATS (+1.34 against expected)
  • With a week off: +2.13 ATS (+2.72 against expected)
Overall, against the spread, they went 123-83-9.  I did notice a lot of volatility in terms of performance against the spread.  Only 51 outcomes were within 5 points of what the spread expected.  A whopping 44 were more than 20 points off the spread.  I don't know the normal volatility ATS, but 20% of games being off by more than 20 points seems like a lot.  The only conclusion I can draw is to avoid betting on these games, because Vegas and other bettors don't really know what to expect.

Does the road trip length matter?  It seems to:
  • 2 time zones away: +2.21 ATS (+2.19 expected)
  • 3 time zones away: +1.26 ATS (+1.04 expected)
And one last breakdown, this time by the road trip outcome:
  • Won on road trip: +1.09 ATS (-0.03 expected)
  • Lost on road trip: +2.12 ATS (+2.64 expected)
Any way you slice it, teams beat the spread when they come home from long road trips.  So, we can ultimately reach one of two conclusions:
  1. Long road trips do not adversely affect a team's chances at home a week later.
  2. If they do, it is already overcompensated for in the betting lines.
In other words, don't blame Tempe.


Special thanks to Tim Peacock for suggesting this study.

Brent Blackwell compiles the NEPA rankings for cfbtn.com.  Follow Brent on Twitter by mashing the pretty button below.


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