Saturday 9 September 2017

Odd Numbers From the NFL

As I mentioned yesterday, the 2017 NFL season is now underway, and I'll be continuing with the NFL Small Road 'Dogs system, which is similar to, but not exactly the same as, its College cousin.

Anyone interested in betting on American Football will soon find out about about the key numbers, 3 and 7.

Three points is, of course, the value of a field goal, while seven points represents a converted touchdown.

Going back to 1989, 6,921 games which is as far back as I have data, the spread has been 3 points a leading 14.75% of the time, while 7 points has been the line 6.87% of the time.

Sandwiched in between these two at 7.97% is the 3.5 point spread, and according to Odds Shark:

The field goal with the hook (-3.5 spreads) is the most fascinating number here. Faves win and cover at far higher rates at -3.5 than they do at -3 or -2.5.
Be careful with this statement. 

"Far higher" is a subjective term. Of course you would expect the rate to be higher for -3.5 point favourites than smaller lines, and indeed this is what the results show, but whether "far higher" is an accurate description is arguable.

For straight up favourites, the results around the -3 point line are:
But the claim is that favourites win "and cover" at far higher rates at -3.5 too. 

Odds Shark's numbers supposedly (more on this later) go back further than mine, to 1984, but my numbers show that at -3.5 points, the spread is covered just 47.4% of the time, fewer than the -3 point spread. 
Odds shark comments further on the -3.5 point spread, writing:
The added half-point to make the line to -3.5 rather than -3 is designed to make the bettor uncomfortable in taking the favorite. The average recreational bettor would happily lay the three points with the cushion of a push floating around in his/her head but they hesitate when that number bumps to three and a half.

What often ends up happening is bettors allow this discomfort to veer them toward taking the underdog. The data says that’s a mistake. Faves cover at a profitable number if you were simply to take the favorites at -3.5 in every game in our database going back to 1984.

So my tip here is to try to embrace the hook rather than fear it when it comes to field-goal spreads. They tend to be decent moneyline sides to throw on a parlay and faves tend to have the edge against the spread here … and sportsbooks know it.
Even if the inclusion of the five years of data from 1984 to 1988 were to make Odds Shark's statement that:
Faves cover at a profitable number if you were simply to take the favorites at -3.5 in every game 
a factually correct one, I'd be wary about going against a trend that hasn't existed in the past 18 seasons.

It's also possible that the different findings are the result of using different data from different sportsbooks, so always check your own sources before acting on anything you read either here or elsewhere.

Odds Shark's numbers compared with mine are below:
Note that it's also a little strange that I would have so many more results (approximately double) from fewer years than Odds Shark. 

My numbers do include the post season games, but that doesn't come close to explaining the discrepancy.

Finally, a gift for the 2017 season. I've mentioned before how keeping an eye on rule changes can be a good way of finding an edge, and the change made after the 2014 season to move back the extra point by 13 yards is a good example. 

Although it wasn't clear how big an impact the rule change would have, it seemed logical to me that at least a few additional extra points would be missed, which was the intent of the rule change. 

In the 2014 regular season, 8 extra points were missed. 

Following the rule change, 71 were missed in 2015, and last season 76 were missed. Total attempts per season are around 1,200.

After two seasons, the secret is probably out by now, but my strategy of betting the underdog to cover 7 point spreads over the past two seasons has a 17-7-2 record, which at a winning percentage of 71% turned out to be one of my better ideas.

Last season (2016) three 7 point favourites won their games by 6 points, most notably the New York Giants on November 20th who played the Chicago Bears in a game in which no less than three PATs were missed, and the Giants won 22:16.

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