I spent 30 years fixing slot machines. Bally slots, IGT slots, Aristocrat slots. Every machine has a computer inside that controls the RNG, the random number generator. The RNG is programmed with a specific payout percentage. An IGT machine might be programmed to return 94 percent of money wagered over a large sample.
In Nevada, the Gaming Control Board required casinos to publish average payout percentages starting in 1965. The reports showed the average RTP across all machines in each casino. A casino might report that their average payout for a month was 93.2 percent, meaning they retained 6.8 percent.
The requirement was not adopted because regulators wanted to protect players. It was adopted because Nevada wanted to show that the casinos were not running at unreasonable edges. At the time, some casino operators were showing RTPs of 88 percent or lower, meaning the house kept 12 percent on average. The reports were a way to make gambling seem fairer.
The Information Asymmetry
A payout report tells you the average, not the range. A casino might report 95 percent average payout, but some machines pay 92 percent and some pay 97 percent. The report does not specify which. A player cannot walk into the casino and be told which machine is which.
The report also covers a historical period. A report covering January shows what the casino's machines paid in January. It does not predict February's payout. The RTP is a theoretical long-term average. Over 10,000 spins, the machine should return approximately its programmed percentage. But most players do not play 10,000 spins. They play 50 spins and lose.
The report serves a regulatory purpose more than a player-protection purpose. Regulators want to know that casinos are not cheating egregiously. The report is evidence that the casino is operating within the industry norms.
A payout report is transparency masquerading as information. It tells you something true without telling you anything useful.
The Modern Report Systems
Online casinos publish payout percentages because their licenses require it. The percentages are usually available on the casino's website under the heading "RTP" or "Theoretical Payout Percentage." A player can see that a specific slot machine has a 94.5 percent RTP.
Unlike Nevada's historical reports, online casinos publish the theoretical RTP per game, not the historical payout per game. These are different. The theoretical RTP is the programmer's specification. The historical payout is what actually happened. Over a small sample, these can differ significantly.
Some jurisdictions require online casinos to publish both theoretical and historical payouts. The UK Gambling Commission, for instance, requires operators to make historical payout data available to players who request it. This is less common than you would expect. Most players do not request this data.
The Strategic Value of Publishing
Casinos publish payout percentages because it builds trust. A player seeing that a machine has a 95 percent RTP might feel more confident playing it, even though 95 percent RTP is still a house edge of 5 percent. The publication of the number makes the game feel regulated and fair.
The publication also protects the casino from accusations of cheating. If a player loses unexpectedly and sues, the casino can produce the RTP report showing that the machine was operating as specified. The report is legal protection more than customer information.
