You’ve seen it time and time again: The home team drives down the court, ball goes to their All-Star center, he knocks two opponents over like bowling pins… no call. At the other end, the defender plants his feet in time, takes the hit… blocking foul. Soft referees – just one of the many perks of playing at home.
So why do the visitors perform so well against the NBA betting odds? According to the Wizard of Odds, road teams cashed in 49.64 percent of the time from 1987 to 2006, compared to 48.37 percent for home teams (the remaining 1.99 percent pushed). However, the gap was a fair bit smaller in 2013, when away teams went 649-643-22 ATS. That’s 49.39 percent for those pesky invaders, 48.93 percent for the home side, and 1.67 percent pushes.
Diminishing Marginal Returns
The gap exists at all because the sports betting market overvalues home-team advantage, of course. Unfortunately for us lazy folk, the margin between home and away isn’t big enough to just auto-bet the road teams. You need to get paid at least 52.38 percent of the time on “even bets” to make up for the –110 juice; after accounting for the pushes, away teams cashed in at a 50.23-percent clip last year. And that’s down from 50.65 percent during the earlier 20-season sample.
Well, that’s not good news. When you bet on the NBA, you want as many advantages in your corner as you can get – a little bit here, a little bit there. You want the small-market, boring-ass San Antonio Spurs on the road against the publicly adored Los Angeles Lakers (the Spurs are 10-10 SU and 12-8 ATS in their last 20 meetings), and not at home (13-7 SU, 9-11 ATS). It’s basic NBA handicapping, really.
Back to School
And maybe that’s what it boils down to. More and more people every year have the extra cash to bet on the NBA, and they’re on the Internet, learning the basics and applying them. You could be one of those people. The veil has been lifted; NBA betting is a competitive marketplace, and the busier it gets, the more this marketplace will achieve efficiency over time. We should expect these margins to grow smaller.
But there are forces acting in the other direction. While more people in the marketplace are becoming aware of the value in betting the visitors, the advantage that home teams enjoy in the real world is shrinking. So says a recent paper from stats professor Tim Swartz and student Adriano Arce at Simon Fraser University, near Vancouver, B.C. They studied the numbers and found home teams were losing their touch across multiple sports.
Swartz and Arce did a fine job of breaking down the specific advantages that can come from playing at home – including playing at high elevation, like the Denver Nuggets and the Utah Jazz. In theory, even this advantage will decrease over time as opposing teams get better at adapting to these situations. But at least in the short term, Denver will remain 5,130 feet in the air.
The bigger question: How long will the referees remain biased? Swartz and Arce point out that major sports leagues are under increasing pressure to make the right call, which “may provide an indication” why home-court advantage is dwindling in the NBA, and therefore merits further investigation. In other words, we need more data on this.
Meanwhile, the idea makes logical sense. The NBA, along with every other major pro sport, is increasingly catering to the fans at home more than the ones attending live. The technology exists where the millions (and millions~!) of people around the world, watching in living rooms and bars on glorious HD screens, can see ever-more instant replays from angles you never knew existed. NBA officials now go to the sidelines to look at these screens, review certain plays and correct certain calls. We are all witnesses. We are all getting sharper. Place your NBA picks accordingly.