The ten most meaningful pointspreads are 1, 3, 4, 6, 7, 10, 11, 13, 14, and 17. (Not in that order) Almost two-thirds of all NFL games can be expected to end with one or another of only those ten margins of victory. Consequently, a bookmaker needs a very good reason to move his line either off or onto one of those ten key numbers. When the bookmaker does move his line from or to one of those ten numbers, it's usually because he's having trouble getting enough action on both sides of the bet.

For you, as a bettor, a line move off one of those numbers can easily present either an opportunity or a trap. An underdog getting 3½ points, for example, is a much better bargain than the same underdog getting only 3 points. That extra ½-point means their opponents must upgrade a field goal to a touchdown in order to cover. And by the same token, an underdog getting only 2½ points is a much higher risk than the same underdog getting 3 points. A ½-point move from a pointspread of 3 can be more important than many much larger moves. An underdog getting 9½ points instead of 7½ points is hardly a better deal at all. Since games rarely end with a margin of victory of exactly 8 or 9 points, there's simply not much difference between getting 9½ points or 7½ points. If an underdog fails to cover 7½ points, they're not likely to cover 9½ points, either. Likewise, a favorite giving away 7½ points is hardly a better bet than the same favorite giving away 9½ points. If a team wins by more than 7½ points, they will almost always win by more than 9½ points.

The importance of different size pointspreads does not increase on an evenly ascending scale. Imagine a very crazy staircase where some steps are much higher than others, and hardly any two steps are exactly the same size. Our natural instincts tell us to place a bet whenever the pointspread is a certain amount different from our own prediction - but that instinct is misleading because of the unique factors involved. For example, if your final forecast shows a 2½-point favorite should win by 4½ or 5 points, there may be a good argument for going with the bet, even though your prediction is only 2+ points away from the posted line. This is because there is a substantial likelihood that the favorite could win by either 3 or 4 points.

On the other hand, if you show a 7-point favorite should win by 9½ or 10 points, you may be well advised to pass the bet. Even though your prediction is further from this pointspread than in the first example, it's a much riskier proposition. Since games rarely end with 8- or 9-point margins of victory, the favorite would very likely have to beat your own prediction in order to cover the 7-point line.

The implications are obvious: It is important to take the time to shop. Shopping for lines is one of your most significance advantages.