How Casinos Actually Win

Modern slot machines don't randomize the reels. They randomize a number, and the reels are a skin. A pseudorandom number generator picks an integer thousands of times a second; when you press the button, the current integer maps to a virtual reel position, and the physical reels then spin to that position. Payouts are determined by a "par sheet," a probability table held by the manufacturer and reviewed by state gaming regulators. Typical Nevada slots are set between 6% and 10% "hold" — the fraction of all dollars in that the house keeps.

Table games are different. Blackjack, played with basic strategy and perfect play, has a house edge around 0.5% on a standard six-deck shoe. Craps pass-line bets: 1.4%. European roulette: 2.7%. American roulette: 5.3%. Every game is a well-characterized negative-expected-value problem for the player, with variance large enough to produce short-term winners and long-term losers almost every time.

What actually keeps the casino solvent is volume, not odds. Bill Eadington, the longtime director of the Institute for the Study of Gambling at UNR, used to point out that a 1% edge looks tiny but compounds over hundreds of millions of wagers per month. A Strip property might see $100 million a month in table drop; the math hands back a few million to the house, predictably.

The business model includes comps. Casinos track every play through loyalty cards and reward high-volume losers with free rooms, meals, and entertainment. The comps cost the house a fraction of what the player is giving them in expected loss. It is a return of a tiny part of the hold, and marketers call it retention. The players call it generosity. It is the most elegant part of the operation.