Over–under: Difference between revisions

As with other types of bets where the odds of either outcome are meant to be even, the [[vigorish]] (or "vig") is typically set at or about 10% of the total wager. Using American odds, this will result in both outcomes initially being quoted at +-110 (i.e. bettors must risk $110 to win $100). If the amount bet on both outcomes is exactly even, using such odds would result in the sportsbook earning $5 in gross profit for every $105 wagered.

Of course, bettors will not necessarily risk the same amount of money on both outcomes every time. In such circumstances, there are two ways a sportsbook can mitigate the risk. The first is to adjust the O/U while keeping the odds of both at +-110. For example, if the O/U for a football game is set at 45.5 and the action heavily favors the "over" then the O/U could be adjusted to 46.5 to encourage bettors to take the "under." The risk here is that the sportsbook could lose alota lot of money by being "middled" - using the aforementioned example, if the final combined score is 46 then the sportsbook would be obligated to pay both the initial bettors who bet "over" and the later bettors who bet "under."

The other method to mitigate risk is to adjust the odds on the initial O/U, which is slightly more complicated but eliminates the risk of being "middled." In the aforementioned example, the "under" could be adjusted to +-105 while the "over" is changed to +-115 (meaning bettors would have to risk $105 and $115 respectively to win $100) in order to make the original "under" proposition more attractive (and the "over" less so) to bettors. In actual scenarios, even adjustments of -100 (i.e. "even money") and +-120 are common place as sportsbooks typically endeavor to maintain steady margins and minimize risk.