NBA Betting Against the Public 2003-05

  • NBA – BETTING AGAINST THE PUBLIC STATS 10/31/2003 – 11/01/2005

About nine months ago, wrote its first article on inefficiencies in the sports betting marketplace. Our first article studied the performance of SI’s “Bet Against the Public” strategy on the NBA, near the midpoint of last year’s season. Since that time, SportsInsights has been pleased to show that our approaches work across various sports, showing good consistency of parameters and results.  Read All Articles On Betting Against the Public

To celebrate the tip-off of another NBA season – SportsInsights has updated the original NBA article with data through the end of last year’s NBA season. The results re-confirm some of the premises that SportsInsights is based upon – and do this with about 33% additional data (increasing the statistical significance of 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 Bet Against the Public

It is a core belief of that inefficiencies exist in the sports betting marketplace. These inefficiencies are caused by the public’s psychological bias toward betting “Favorites.” Nobody likes betting on bad teams. It’s even harder for us to bet on horrible teams – but it is exactly this phenomenon that produces a sizeable bias in the sports marketplace. The SportsInsight’s series of articles demonstrates that inefficiencies exist in the sports betting market and describes strategies for exploiting these inefficiencies.

It is impossible to predict the future. It IS possible, however, to use statistical analysis and risk modeling to test for profitable opportunities in any marketplace. There is a fallacy that exists in the sports betting world. Sportsbooks do NOT look to balance action on their books. Oddsmakers know that the public disproportionately bets on Favorites. They factor this bias in when they create betting odds and lines. It is this “public bias” (betting on favorites) that we look to measure.

NBA Betting Against the Public: 10/31/03-6/30/05

We used NBA game data from’s database for the past two seasons. This covers about 2,500 games. Various data checking methods were used to eliminate bad data and ensure cleaner, more reliable results. We evaluated the “Bet Against the Public” strategy using the Public Betting Percent threshold, based on an average of the Straight Bet Public % and Parlay/Teaser Public %.

Table 1 looks at the results if a person bets on a team with X% (Public Bet %) or lower.  As you can see, if the public does NOT like a team at certain extremes, SportsInsights members can achieve a meaningful edge.

Table 1:  NBA Bet Against the Public (10/31/03-6/30/05)

X% or Lower (Public Bet %) # Games Win % Avg Margin Win Avg Margin Loss
50 2,410 50.7% 9.3 8.4
45 1,763 50.6% 9.3 8.3
40 1,215 51.2% 9.3 8.3
35 756 50.5% 9.4 8.5
30 415 53.7% 9.4 8.4
25 191 51.8% 9.1 8.6
23 122 54.9% 9.2 7.6
20 60 55.0% 8.9 6.9
15 12 66.7% 6.2 5.6
10 3 66.7% 5.3 0.5