If one team is receiving a large majority of the bets on a particular game, the sportsbook will move the point spread to try and attract bets on the other team, as well as to discourage additional wagers on the popular team. If the Miami Heat are favored against the spread by 7 points in a game and almost all the bets are coming in on Miami, the spread will likely change to Miami -8. If that doesn’t stop the bets from coming in on Miami, the spread could move to Miami -9 or higher.
At times, a bettor will be required to risk $115, $120, or possibly more to win $100 when betting with the point spread. This will occur most often in football games when the spread is on one of what are known as the “key numbers.” In football, these are typically thought of as 3, 4, 6, 7, and 10, as teams are much more likely to win by one of those margins than they are by, say, 5 or 9 points.
If the Miami Dolphins are favored by 3 points over the New York Jets and a large percentage of the wagers is coming in on the Dolphins, the sportsbook may be hesitant to move the odds to Miami -3.5 or Miami -4 for fear of receiving too many bets on the Jets. Even if the point spread moved only a half-point, to Miami -3.5, and the bulk of the bets transition to the Jets, the worst thing that could happen from the sportsbook’s point of view would be for the Dolphins to win by exactly three points. If they did, the many bettors who had already taken Miami -3 would tie their bets, while those who’d taken the Jets +3.5 would win their bets, which would cause the sportsbook to lose a fair amount of money on the game.
So instead of moving the point spread off of one of the key numbers, many times the sportsbooks will move the odds so that those who want to wager on the Dolphins will be asked to risk $115 to win $100, while those taking the Jets will risk $105 to win $100. If the odds changed to where those betting the Dolphins were asked to risk $120 to win $100, those taking the Jets would risk $100 to win $100.
It’s important to note that while odds are based on $100 wagers, you don’t have to wager that much. In the example where Miami bettors risk $120 to win $100, you could just as easily wager $24 to win $20. It’s simply easier to refer to bets in terms of $100.
Point spreads can also move due to issues such as injuries, suspensions, and weather. A team without its starting quarterback or leading scorer won’t be expected to perform as well without the player as with, while a driving snowstorm can slow down a high-powered offensive team.