Point spreads focus on a margin of victory between the two teams and again, what you’re looking for is the positive and negative signs. If there is a minus sign next to a team’s spread, that suggest that they are favored and have to win by or cover that amount. If there is a positive sign, that tells you that they are the underdog and they are getting points. For example: let’s say that the New England Patriots are playing the Buffalo Bills and the Patriots are -5.5 and the Bills are therefore +5.5. If you bet the Patriots, they have to win by six points or more to cover. If you bet the Bills, they can lose by five points or less, or they can win the game outright and you would still win your bet.
The number that follows the plus or minus sign will indicate how big of a favorite or an underdog the team is. The larger the number is, the bigger the favorite or the underdog the team is. For example, a team that is -300 is a bigger favorite than a team that is -150. A team that is +240 is a bigger underdog than a team that is +130. Remember, this is not the sportsbook’s actual prediction on who they think will win; it’s in relation to the money that has been bet on the game. It is more depictive of who the betting public thinks is going to win the game.
Let’s say that the Mavericks and the Magic are playing in an upcoming game, and both teams are equal counterparts. Let’s say that the odds for that game are as follows. You will never see these odds, though, because in this example, the sportsbook is not set to make any money if they achieve their goal of getting money on both sides of the bet. But we need to look at it for you to better understand things.
The optimal situation for bookmakers is to set odds that will attract an equal amount of money on both sides, thus limiting their exposure to any one particular result. To further explain, consider two people make a bet on each side of a game without a bookmaker. Each risks $110, meaning there is $220 to be won. The winner of that bet will receive all $220. However, if he had made that $110 bet through a bookmaker he would have only won $100 because of the vig. In a perfect world if all bookmaker action was balanced, they would be guaranteed a nice profit because of the vig.
Oddsmakers want you to gamble on underdogs as well as favorites. They set points spreads that encourage balanced betting. They analyze the strengths and weaknesses of each team, factoring in won-loss record, strength of schedule, results against common foes, key injuries, recent performance and previous games between the teams. They also rate the value of home field advantage and consider the game day weather forecast where relevant. If they see heavy wagering on the favorite, they will increase the point spread during the week to spur more betting on the underdog. If more money is going on the underdog, the spread will decrease as game time nears.
Having set the point spread, this is the point where the gambling public can influence the line. You might have noticed that a line five days before a game might look very different to the line an hour before the kickoff. Barring some major line-up changes due to injuries or suspensions, the line will most likely be moved by weight of money. If the majority of money is coming in on one side of the point spread, the book will move the line to make the bet a little less attractive, which will help them level the book up somewhat.
One important assumption is that to be credited with a win, either team only needs to win by the minimum of the rules of the game, without regard to the margin of victory. This implies that teams in a winning position will not necessarily try to extend their margin—and more importantly, each team is only playing to win rather than to beat the point spread. This assumption does not necessarily hold in all situations. For example, at the end of a season, the total points scored by a team can affect future events such as playoff seeding and positioning for the amateur draft, and teams may "run up" the score in such situations. In virtually all sports, players and other on-field contributors are forbidden from being involved in sports betting and thus have no incentive to consider the point spread during play; any attempt to manipulate the outcome of a game for gambling purposes would be considered match fixing, and the penalty is typically a lifetime banishment from the sport, such is the lack of tolerance for gambling in sport.
Sports betting has been around since 1000 B.C in China, where betting on animal fights was commonplace. In ancient Rome, one could wager on the Gladiatorial games. The idea of betting on sports is as old as organized sport itself. But up until the 1940s, bettors were fairly limited in what kind of bets they could make. The standard system of odds would allow bets on, for example, the 3-1 odds that the Steelers would beat the Browns.