Bookmaker

A bookmaker (or "bookie") is a licensed entity that accepts bets on the outcome of events, sets the odds, and pays out winners. The business model rests on the margin built into the prices — the vig (also called overround or juice) — which ensures that, across balanced action, the bookmaker keeps a share of the total staked regardless of the result. The key to understanding a bookmaker is the overround. The prices on a market imply probabilities that deliberately sum to more than 100%; the excess is the bookmaker's theoretical profit margin. Worked example: on a two-way market a bookmaker prices each side at 1.90 rather than the fair-coin price of 2.00. Each 1.90 implies a probability of 1/1.90 = 52.6%, and the two sides together imply 52.6% + 52.6% = 105.3%. That 5.3% overround is the bookmaker's built-in edge. If equal money is taken on both sides, the book pays out less than it collects whichever side wins — the definition of a balanced, profitable position. Why it matters: every price you take already carries this margin, which is why beating a bookmaker over time requires consistently finding odds longer than the true probability. How bookmakers manage risk: they aim to balance liability across both sides of an event and adjust odds as money arrives, shortening the well-backed side and lengthening the other to steer action and protect the margin. Major global operators include bet365, William Hill, Betway and others. Common mistake: assuming the displayed odds reflect the true chance of an outcome. They are shaded by the overround and by where the bookmaker wants money to land, not a neutral estimate. Compare to: Vig, Implied Probability, Betting Line.