Generally speaking, recreational NFL bettors like cheering for points. In fact, in 4,451 games in the Bet Labs database, the over has received a majority of bets in 3,787 games (85.1%) since 2003.
Oddsmakers know the public tends to bet the over. As a result, bookmakers shade the line, which creates value for contrarian gamblers to bet the under.
When the line increase by at least one point, the under has gone 613-588-21 (51.0%) since 2003. In high-total games (45 or more points) during the same time, unders are 895-818-23 (52.2%).
Neither trend in itself is profitable, but combined an interesting trend emerges. Since 2003, in high-total games when the over/under increases by one or more points the under has gone 346-309-10 (53.0%).
It is optimal to follow this system in the second half — Weeks 9-17 of the season:
This system is profitable for a few reasons. First, it is easier for an under to hit in a high-total game. Second, late in the season offenses are more likely to be dealing with injuries because of the wear and tear of a 16-game schedule, which would limit their effectiveness and thus lower the scoring output.
On Monday Night Football, the Vikings-Seahawks total opened 49 and has been bet up to 49.5, making the under a match for our system.
And in addition to history being on the under's side, so too is our projected total. According to our model, the Vikings and Seahawks should combine for an average of 47.6 points, making the under an even more appealing play.
