# Pointspreads Explained: How bookmakers set the betting line

Spread betting was invented by Charles K. McNeil, a math teacher from Connecticut who became a bookmaker in Chicago in the 1940s. The bettor bets that the difference in the scores of two teams will be less than or greater than a value specified by the bookmaker.

For example, if a bettor places a bet on an underdog in an American football game when the spread is 3.5 points, he is said to take the points; he will win his bet if the underdog's score plus 3.5 points is greater than the favourite's score. If he had taken the favourite, he would have been giving the points and would win if the favourite's score minus 3.5 points was greater than the underdog's score.

As you all know, when you place a straight wager on the pointspread of a football or basketball game, you need to risk \$110 to win \$100. The \$10 difference between risk and payout is known as the juice, or the vigorish, or “vig” and is the reason sportsbooks are in business. Sportsbooks essentially act as a broker between you and another player who wants to bet on the other team and collects the small commission as compensation for brokering the deal and handling the transfer of funds between the two of you. This is important to understand, because it leads me to the biggest misconception in sports wagering. The pointspread is not the handicapper’s predicted margin-of-victory, but it is in fact the handicapper’s prediction of what number will be required to split the wagering evenly on both teams. Understanding that little tid-bit is the first step towards taking advantage of the numbers.

"Linemakers," says former BoDog chief Rob Gillespie, "are divided into two groups, oddsmakers and bookmakers".

Oddsmakers deal in a theoretical world because they don't actually take bets on the lines that they publish. Oddsmakers make their money by selling their lines to media outlets, sportsbooks, etc. These are the lines you see in your local newspaper or hear on the radio. The line from Las Vegas Sports Consultants is a good example of one of these. The LVSC line is the one distributed to Las Vegas Sportsbooks. The lines don't change very much from day to day, because there are no direct wagers placed on these lines, and as such, there are no line moves required to try and balance action.

On the other hand, bookmakers deal very much in the real world, as they take bets on the lines they publish. These lines then move as a result of wagering, because the books seek to balance action in an effort to minimize risk and maximize the vig collected. This fundamental difference is one of the main reasons that the lines you see in your newspaper are not the same lines you get when you deal with a sportsbook. It is worth mentioning that time is also a factor. The lines in your paper were probably accurate when they were submitted to the editor, but in the amount of time that passes from pre-production to when you read the paper, injuries, weather and other factors can dramatically shift the spread.

Linemakers use a variety of methods to calculate their idea of the pointspread. Some use complicated computer programs that factor in recent performance, injuries, player match-ups, etc. Others simply have a feel for the games and produce a number out of thin air. However, most line makers use power ratings or some derivation.

Power ratings involve assigning each team a numerical value based on performance and than comparing the ratings to generate a pointspread. For example, one set of ratings I saw this week had Miami rated 57 at home and Indianapolis rated 53 on the road, so the difference results in a 4 point line. Another set has Miami rated 77, Indianapolis rated 75, and gave a 3.5 point advantage to the home team so it predicted an opening line of 5. The actual line opened at 6 at some books, and was bet down quickly to 4.5, so it appears that 6 was too high. There are no standards for how to derive these ratings, and predicting actual outcomes with better accuracy than the majority of the betting public is your key to success.

Some sportsbooks base all their lines on their own internal linemaking, but the majority of books rely either solely on oddsmaking services or a combination of external service and their own handicapping. BoDog Bookmakers handicap the games themselves, compare these results to the opening lines out of Vegas and then adjusts for the historical action of their own player base before coming up with a consensus opening number for each game. From there, the numbers are moved only to balance action or to account for special circumstances such as weather, injuries or the like.

The key advantage bettors have is that they do not have to wager on every game, but can pick and choose wagering opportunities. The bookmaker however, puts up a number on hundreds of events each and every week. In a typical NFL week, there are 14 to 15 games for you to choose from and there are even multiple betting opportunities on each game. You may not have a good feel for every game, but you most likely see several games where you are confident that one team will cover with better than 53% probability. This is what handicappers refer to as an "overlay" or "getting value", which is the starting point of every handicap.

by: Winning Inc. - SpreadExperts.com - Email Us

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