Bet on Sports!
By adjusting the odds in his favor or by having a point spread, the bookmaker will aim to guarantee a profit by achieving a 'balanced book', either by getting an equal number of bets for each outcome, or (when he is offering odds) by getting the amounts wagered on each outcome to reflect the odds. When a large bet comes in, a bookmaker can also try to lay off the risk by buying bets from other bookmakers. The bookmaker does not generally attempt to make money from the bets themselves, but rather profiting from the event regardless of the outcome. Their working methods are similar to that of an actuary, who does a similar balancing of financial outcomes of events for the assurance and insurance industries.
What are odds?
In gambling, the odds on display do not represent the true chances that the event will occur, but are the amounts that the bookmaker will pay out on winning bets. In formulating his odds to display the bookmaker will have included a profit margin which effectively means that the payout to a successful punter is less than that represented by the true chance of the event occurring. This profit is known as the 'over-round' on the 'book' (the 'book' relates to the old-fashioned ledger that wagers were recorded in and thus gives us the term 'bookmaker') and relates to the sum of the 'odds' in the following way:
In a 3-horse race, for example, the true chances of each of the horses winning based on their relative abilities may be 50%, 40% and 10%. These are the relative probabilities of the horses winning and are simply the bookmaker's 'odds' multiplied by 100 for convenience. The total of these three percentages is 100, thus representing a fair 'book'. The true odds of winning for each of the three horses is Evens, 6-4 and 9-1 respectively. In order to generate a profit on the wagers accepted by the bookmaker he may decide to increase the values to 60%, 50% and 20% for the three horses, representing odds of 4-6, Evens and 4-1. These values now total 130, meaning that the book has an overround of 30 (130 − 100). This value of 30 represents the amount of profit for the bookmaker if he accepts bets in the correct proportions on each of the horses. The art of bookmaking is that he will take in, for example, £130 in wagers and only pay £100 back (including stakes) no matter which horse wins.
Profiting in gambling involves predicting the relationship of the true probabilities to the payout odds. If you can consistently make bets where the odds of paying out are better (pay out more) than the true odds of the event, then over time (in theory) you will come out ahead.
The odds or amounts the bookmaker will pay are determined by the amounts bet on each of the respective possible events. They reflect the balance of wagers on either side of the event, and include the deduction of a bookmaker’s brokerage fee.
