A bookmaker strives to accept bets on the outcome of an event in the right proportions
in order to make a profit regardless of which outcome prevails. See Dutch book and coherence
(philosophical gambling strategy). This is achieved primarily by adjusting what are
determined to be the true odds of the various outcomes of an event in a downward fashion
(i.e. the bookmaker will pay out using his actual odds, an amount which is less than the
true odds would have paid, thus ensuring a profit).
The odds quoted for a
particular event may be fixed but are more likely to fluctuate in order to take account of
the size of wagers placed by the bettors in the run-up to the actual event (e.g. a horse
race). This article explains the mathematics of making a book in the (simpler) case of the
former event. For the second method, see Parimutuel betting. (資料來源)
