NFL First Halves

King Yao is the author of Weighing the Odds in Hold‘em Poker, and Weighing the Odds in Sports Betting. He uses his experience from making millions in financial derivative markets and translates it into gambling. Since he left his trading position in 2000, he has been playing poker and betting on sports. He travels to Las Vegas frequently, especially during football season.

The NFL first-half bet has been popular for a while; it was one of the first derivative wagers offered that did not depend on the final outcome of the game. The interaction between line makers and bettors over the years has reduced the number of profitable opportunities, but there are still some good bets to be made.

Just as small home underdogs have historically covered the game point spread more often than small home favorites have, small home underdogs have also covered the first-half point spreads more often. For example, a -2 home favorite covers a -1 first-half line at a rate equivalent to +102; but a +2 home underdog covers a +1 first-half line at a rate equivalent to -133. For example, if a pick ’em line in the first half is -125, then the bet has a 9.5% chance of being a push and resulting in a refund. The standard error on that 9.5% is 1.2%, so think of the 9.5% as meaning somewhere in the interval of 8.3% to 10.7%. The value of a half point around pick ’em is 21 cents, with a standard error of 3 cents. Thus if a pick ’em line in the first half is -125, then the -0.5 line should be somewhere around -101 to -107, and the +0.5 line should be somewhere around -143 to -149.

The Value of Particular Numbers

Frequencies of score differences at the half differ considerably from the full-game frequencies.

Tied at the half

There are no 0.5 full-game NFL lines because ties are rare. Lines will move from pick ’em to -1 or to +1 and skip -0.5 and +0.5. But ties are not rare at the half; 9.5% of NFL games predicted to be close (and 9.1% of all NFL games) are tied at the half.

Sportsbooks may differ in their first-half line with some books using a pick ’em line while other books using a -0.5 or a +0.5 line. Because of the high percentage of games tied at the half, there is tremendous value in getting an extra half point (or not laying the extra half point).

3-point lead at the half

The favorite winning by 3 is by far the most common full-game result. Leading by 3 at the half is not as common. The 5.6% push percentage for the 3 is one of the highest in the first half, but it pales in comparison to the push percentage of 10.2% for the full game.

First-half lines close to 3 are common. One sportsbook may have the first-half line at home team -3 -110, while another may have it at -3.5 +100. Table 9 shows that the value of a half-point when the home team is -3 in the first half is 12 cents plus or minus 2 cents; so it likely is worthwhile to lay the extra juice and take -3 -110.

Other valuable numbers

The first-half push percentages for the 4 and 7 are both high: 5.9% for the 4; and 8.8% for the 7.

The push percentages for the 4 and 7 are both significantly higher in the first half than for the game.

This is part of an occasional series of articles.

Excerpted with permission from the e-book version of Weighing the Odds in Sports Betting by King Yao, edited for this format.