Betting Against the Public in the NBA (Last Five Seasons, ending June 2008)
The NBA remains one of SportsInsights’ most consistent sports. However, as we have seen in various “sports-seasons” — there is a lot of “noise” and variation in short term results. Last season, SIs’ NBA Square Plays slipped to 51.3% after achieving more than a 54% winning percentage in the previous four seasons. Our data on Public Betting Percentages mirrors the results of our NBA Square Plays, finding value at the “20%-23% level,” as we see below. Let’s see how the 2007-08 season impacts our overall results. The information on this site is for entertainment and educational purposes only. Use of this information in violation of any federal, state, or local laws is prohibited.
NBA Data 2003-2008
The SportsInsights NBA database now includes four complete season’s worth of data. Here are some notes on the data we used for this article:
- Data for the past five seasons (November 2003 through June 2008)
- Includes the regular season and playoffs
- Excludes pre-season and All-Star Games
- Almost 6,500 games.
Betting Against the Public — NBA
We are pleased that increasing our dataset about 30% (from about 5,100 games to almost 6,500 games) verifies the results we have seen previously. The increased data strengthens SportsInsights’ view that Betting Against the Public can be an effective way of obtaining value in the NBA Sports Marketplace. More specifically, if we see less than 23% of the bets on one team, it means that the public might be undervaluing that team. Results at the 20% level have a higher winning percentage, but many fewer games.
Table 1: NBA and Betting Against the Public (Last Five Seasons, ending June 2008)
| Betting % | Win % |
| 40% | 50.8% |
| 35% | 50.3% |
| 30% | 51.5% |
| 25% | 50.9% |
| 23% | 52.8% |
| 20% | 54.4% |
SportsInsights’ Square Plays
SportsInsights’ Premium Pro Members have access to our Square Plays. SportsInsights uses proprietary information and sportsbook contacts to highlight plays that have excessive “Square” action — and thus should yield value by “betting against” the square bettors. The performance of our Square Plays, often the most “lopsided-bet games” in terms of both number of bets and money bet — has been positive across all major sports.
As we mentioned above, basketball has been one of our most consistent sports in terms of both “Betting Against the Public” and “Square Plays.” As we updated the statistics this year, we were pleased that performance has remained consistently positive across all the major sports! Below is the average performance of our Square Plays — for spread sports. Note that Square Plays for moneyline sports like baseball and the NHL had good years in 2007-2008 and have been positive, on average.
Table 2: SportsInsights Square Plays – Average Performance by Sport (Since Inception)
| Sport | Square Play Win % |
| NBA | 54.0% |
| NCAAB | 52.5% |
| NFL | 56.0% |
| NCAAF | 57.0% |
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Disclaimer
We do not guarantee that the trends and biases we’ve found will continue to exist. It is impossible to predict the future. Any serious academic research in the field of “market efficiencies” recognizes that inefficiencies may disappear over time. Once inefficiencies are discovered, it is only a matter of time before the market corrects itself.