When the line on a game moves – it can be classified as something which is either REACTIONARY or ANTICIPATORY.

REACTIONARY line moves, by and large, are reflections of the betting patterns on the part of the public. For example, in our Dallas-NY Giants model, let’s say Dallas OPENED as a three-point favorite, but the public bet the Cowboys excessively. With an abundance of money on the Dallas side, the oddsmaker, who has a pre-set limit to the exposure the sports book will experience at any single number, will MOVE the line to try and attract more money over to the Giants’ side, to reduce the sports book’s risk and at the same time get closer to balancing the action on both teams. So he might move Dallas to a 3-1/2 point favorite, then, if that number continues to be laid to a certain level, the number may then be moved to 4 points. Conversely, if there was excessive money bet on the Giants, the number might be moved to 2-1/2, then 2. The greater the overall line move, generally speaking, the greater the disparity of money which had been wagered between the two teams, and in turn, the greater the desire on the part of the sports book to encourage action the other way, for the purpose of balancing the action. It must be stressed that almost without exception, this kind of line move comes in half-point increments on NFL lines, which are traditionally “tighter”; on college lines, where large point differentials are not unusual, the line moves are more volatile, and can move in larger increments.

To show the incremental nature of how the line moves in the NFL, look at a Saints-Patriots game from back in 2005. The OVER/UNDER line on the game (the total points scored between the two teams) opened at 45, and closed at 48-1/2. But it didn't jump to that figure. Instead, it stopped at every half-point interval in between - 45-1/2, 46, 46-1/2, 47, 46-1/2 and finally 48.

For later that week in college football, the Pittsburgh-West Virginia game opened at 9, then jumped to 10-1/2, then was 13 by Sunday night.

These moves, whether they be in the pro or college game, take place as a result of betting action reaching their "game limits," which are pre-determined figures that, once met, will move the pointspread. With regard to the NFL, the sportsbook will move the line up a half-point every time the game limit is reached. The concept of game limits is an interesting and intriguing, and is well worth studying.

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