When sportsbooks first post odds for a game, those odds are referred to as the opening odds. By the time Game Day rolls around, those odds will change. They might not change much, but they will probably change.
The only question is why. To examine that question, let’s take a look at the opening and closing betting lines for Super Bowl LV:
|Game Odds– Super Bowl LV|
|Opening Odds– DraftKings|
|Kansas City Chiefs||-3.5 (-106)||-175||O 57.5 (-107)|
|Tampa Bay Buccaneers||+3.5 (-115)||140||U 57.5 (-114)|
|Closing Odds– DraftKings|
|Kansas City Chiefs||-3 (-110)||-157||O 56.0 (-110)|
|Tampa Bay Buccaneers||+3 (-110)||+139||U 56.0 (-110)|
There was not much movement, meaning the odds did not change much from the opening to the closing lines. But they did change. As for why— there are a few common reasons why odds change:
- New information
- Market Confidence
How Does New Information Impact Why Odds Change?
When the opening odds get posted, oddsmakers do so with the most up-to-date information (player health/availability, weather conditions, etc.) available. But over the course of the two weeks leading up to the Super Bowl, that information may change.
When it does, oddsmakers must take that new information into consideration. The Chiefs would not have remained the favorite if Patrick Mahomes went down with an injury in practice. If Tom Brady had failed a COVID test, the spread would have gotten a lot longer.
It all depends on what the information is and its potential impact. If it is significant enough, then the line will change.
How Does Market Confidence Impact Why Odds Change?
There was a ton of confidence in the Kansas City Chiefs winning Super Bowl LV heading into the 2020 regular season. They were installed as the early favorite when odds were posted and remained so throughout the season.
When oddsmakers set the opening line for the game, it was not surprising that the Chiefs were the early favorites. Confidence was high on the Chiefs, and understandably so. But as time went on, many fans and analysts began to express their belief in the Buccaneers and Tom Brady. The popular opinion went from the Chiefs are going to win to this could be a good game.
As confidence in the Chiefs drops, it becomes less of a certainty that they will win. Consequently, people bet less. This forces sportsbooks to alter the odds so that the uncertainty goes away.
This could mean making the spread bigger or smaller depending on where books want people to bet. Whatever they do, sportsbooks must give bettors a reason to feel confident in which team they put their money on.
Because in the end, it is all about the money.
How Does Money Impact Why Odds Change?
Sportsbooks go into business for the same reason people bet—to make money. To that end, sportsbooks ensure that they will turn a profit by collecting a commission on losing bets known as the “vig.”
The vig is essentially what the sportsbook charges to take a bet. So, what is it? When you see odds of +110 posted for a bet, the “10” is the vig. If you wanted to win $100, you would have to risk $110.
So, if the vig is how sportsbooks make money, that means sportsbooks must do what they can to take in equal amounts of money on both sides of a bet. But if one team is a heavy favorite and public confidence is high on that team, how do sportsbooks do it?
Easy—by making putting money on the other team a good bet. How do they do that? They change the odds to give the other side of the bet more value.
Why Odds Change—FAQs
No, they are not. Odds get adjusted on an individual basis according to what each sportsbook needs.
Line shopping entails checking various sportsbooks to see who has better odds for the game/event you are interested in. For Super Bowl LV, some books had the Chiefs at +3 while others had them at +3.5. Had they won by three, bets at +3 would not have won—but the ones at +3.5 would have.
That is a strategy you could take. But keep in mind that the odds could change in a way that is not beneficial to how you want to bet. A game that opens at +/-3 could close at +/- 1. For a game that is expected to be close, having three points is better than one.