Many people think that the point spreads show what oddsmakers believe are the numbers of points a favorite will win by. However, this is not the case. The goal of a point spread is to attract an equal amount of bets on either side. Oddsmakers want to create numbers that will cause half of people to place bets on one side while the other half bet the other side. This is called dividing the action, which means the sportsbook or bookmaker is guaranteed to receive a profit on the bet no matter which side wins.
An opening line is the first line that oddsmakers create and send out to online sportsbook companies, casinos and bookmakers. The opening line is created from a power rating based on the value of each team. These power ratings are used to calculate a preliminary point spread for the next game. Whenever a team finishes a game, the power ratings are adjusted. Other non-game factors such as player injuries and trades will also cause the power ratings to become adjusted.
After a point spread is determined based on the power rating then the line is adjusted once the most recent games are reviewed. Adjustments can also be made based on what a newspaper prints about a coach or players thoughts at the start of a game.
Since the purpose of a betting line is to divide the action, the oddsmakers also take into account what the public thinks of the team and current betting patterns. After the opening line is released by the oddsmakers then the individual bookmakers or sportsbook company can decide to adjust the line before they post it for their players to view. This is to divide the action more evenly.
After betting has started, the line can change at any time. By doing this the sportsbook can make a team look more attractive so they will get more action. This also allows them to influence the way the public bets on a certain game.