180Gambler > History
A history of betting and bookmaking
Field: History. This page was last modified on 17 August 2026.
Wagering on the outcome of a contest is older than any record of it, but bookmaking, the business of quoting a price on every outcome and standing behind all of them, is comparatively recent. It appears in the late eighteenth century, and almost everything about modern betting follows from the two competing ways of organising it that emerged afterwards.
Wagers before bookmakers
Early organised betting on horse racing was a matter of private agreements. Owners and their circles matched wagers with each other at agreed terms, often recorded in the same club rooms where the racing itself was arranged. There was no third party taking positions on every runner, and consequently no continuous price on anything. A person who wanted to back a horse had to find someone willing to take the other side at a price they could agree.
The limitation is obvious in hindsight: the market was small, illiquid and closed. The innovation that opened it was someone standing ready to quote a price against every runner in the field at once, accepting stakes from anyone, and balancing the resulting book.
The book and the overround
A bookmaker's price on each outcome implies a probability, computed as described in probability and odds. Added across every outcome, those implied probabilities come to more than one. The excess is the overround, and it plays exactly the role that the house edge plays in a casino game: it is the margin built into the prices rather than into the mechanism.
| Outcome | Fractional price | Decimal | Implied probability |
|---|---|---|---|
| First | 1/1 | 2.00 |
0.500 |
| Second | 2/1 | 3.00 |
0.333 |
| Third | 4/1 | 5.00 |
0.200 |
| Total | 1.033 |
The book above is priced at an overround of 3.3%. A bookmaker who takes stakes in
proportion to those implied probabilities keeps that percentage regardless of the result, which is why the
business is described as balancing a book rather than predicting outcomes. In practice stakes never arrive in
those proportions, so prices move as money comes in, and the movement is an attempt to bring the book back into balance.
The pari-mutuel alternative
The second model removes the bookmaker's position entirely. In a pari-mutuel pool, invented in 1867 by Joseph Oller, all stakes on a race go into a common pool, a fixed percentage is deducted, and the remainder is divided among the winning tickets. The operator's share is stated in advance and does not depend on the result at all.
The two models produce genuinely different products. Fixed odds give certainty at the moment of the wager and leave the operator carrying the risk. The pool gives no certainty, because the final price is not known until betting closes, and leaves the bettors carrying each other's risk. Different jurisdictions came to opposite conclusions about which should be permitted, and several permitted only the pool on the grounds that it removed any incentive for the operator to influence the event.
Notation
The two dominant notations reflect the two models. Fractional odds, in which 5/2 means
five profit for two staked, grew out of the negotiated wagers of the ring and remain associated with fixed-odds
racing. Decimal odds, in which the same price is 3.50, grew out of pool systems where the
natural quantity is total return per unit and where dividing a pool produces awkward fractions. American
moneyline notation, quoting the stake required to win a hundred or the profit from a hundred staked, is a third
convention for the same information.
All three describe the same underlying probability, and the conversions are elementary. Confusion between them is nonetheless common enough that a price quoted without its notation is genuinely ambiguous.
Regulation of the ring
The organisational history is inseparable from the legal one. Nineteenth-century British legislation, in particular the Betting Houses Act of 1853, suppressed fixed premises for betting while leaving wagering at the racecourse itself untouched, a distinction that shaped the trade for a century and pushed a large volume of business into illegal street betting. The eventual legalisation of licensed betting offices in Britain in 1960 was, like the lottery revivals described in the lottery article, largely an admission that prohibition had produced an unregulated market rather than no market. That thread is followed in the regulation article.