By John Grochowski

Maggie is a friend of a friend of my wife’s, someone I met at as holiday party when someone told her I was just the person she needed to talk to about slot machines.

“Tell me how to win,” she said, and I laughed. That’s the most common request I get about slot machines, and it’s one I can’t fulfill. There’s nothing you can do to change the results determined by a machine’s random number generator.

“All right then. Tell me something. I was in a casino last week, and they had a sign up that said ‘Our slots pay back 93 percent.’ Does that mean every machine pays 93 percent?”

No, it doesn’t, I told her. Each casino has a wide range of payback percentages within its game mix. By and large, higher denominations give more money back to players — dollar machines pay more than quarters which pay more than nickels which pay more than pennies.

Even within the same denomination, there’s room for a range of paybacks. In a casino whose nickel games return 89 percent of money wagered to players, there’s likely to be games that pay in excess of 90 percent, and games that pay 85 or 86 percent.

For that matter, it’s possible for games of the same denomination and theme to have different payback percentages. A quarter Red, White and Blue machine that returns 93 percent could sit right next to one that returns 89 percent. That’s not as common as it once was, but the game chips to make that possible are available to casinos.

“So if there are all those different paybacks, how can they say, ‘Our slots pay back 93 percent’? Where does that come from?”

That depends. Was it a plaque on a wall somewhere? Was it a sign over a particular bank of machines?

“It was on a wall, not really next to any particular games.”

OK, I’ve seen that in a few casinos, but not everywhere. It’s a casino-wide average. The total of all money won by the casino at all electronic gaming devices — including video poker, video keno and video blackjack as well as slot machines — is divided by the total number of wagers at those games. Multiplied by 100, that gives us a casino hold percentage. Subtract that from 100, and you have the payback percentage to players.

For example, if \$1 million is wagered on a casino’s electronic gaming devices, and the casino keeps \$70,000, dividing that \$70,000 by \$1 million give you .07, which multiplied by 100 tells us the casino kept 7 percent of all wagers. Subtract that from 100, and we find that 93 percent of money wagered has been returned to players. That’s the payback percentage.

“But not every machine is paying 93 percent?”

Right. Some payback percentages will be in the 80s. Some will be in the high 90s. Most will be in between. Most of the low-denomination slots will pay less than 93 percent. Most of the high-denomination games will pay more. But the casino-wide average in the casino where Maggie plays will come to 93 percent. Other casinos will have their own averages.

“I don’t suppose you could tell me how to tell which games have the better paybacks.”

I’m afraid not. Two slot machines that look identical on the outside can have different payback percentages.

She sighed.

“Oh well. Trial and error it is. At least keep your fingers crossed for a jackpot for me, will you?”

Will do.

Maggie was asking about a sign that listed a casino-wide average, but sometimes you’ll see a sign over a bank of machines that says, “95 percent payback,” or “Up to 98 percent payback.”

Such signs refer specifically to that bank of machines. If it’s specific, with no qualifiers, such as “95 percent payback,” most states require that all machines in the bank be programmed for 95-percent return. There’s room for some short-term variation. If you sit down at a 95-percent machine and have a cold streak, running through a hundred bucks with zero return, there is no requirement that the next player get back 190 percent to even things out. Over time, with enough play, your cold streak will simply fade into statistical insignificance, overwhelmed by the results of hundreds of thousands of reel spins.

Conversely, if you hit a big jackpot, there is no requirement that the machine then go ice cold to get down to the 95 percent target. The machine will keep operating as normal, and over time your jackpot will be overwhelmed by hundreds of thousands of plays and fade into statistical insignificance.

When the sign does have a qualifier, such as “Up to 98 percent payback,” then let the player beware. At least one machine in the bank is likely to be a 98-percenter, but others can be lower. Not all states permit such fudging, and this ploy isn’t as common as it was a decade ago, but when you see it, be wary.

John Grochowski writes a syndicated newspaper column on gambling,
and is author of  the “Casino Answer Book” series from Bonus Books.

### Comment ( 2 )

• Will Black

I have a question about the RNG or Random Number Generator.
My understanding is that the RNG is spitting out 10,000 numbers, in combination arrays (most common is in an array of 5 or 15, depending on the machine type. Keno machines may be set to 20?), EVERY single second!
Is this true? If so, that means 60 * 10,000=600,000 numbers Every Minute!
As long as the slot machine is powered up, that RNG will continue to spit out 10,000 numbers every second of every minute 24/7/365 (unless it’s powered off, of course), right?
Also, what the slot player sees on the machine display screen is all for show, because as soon as the button is pressed/pushed or the slot arm is pulled, the array is chosen.
The rest is just entertainment for the player to be fixated to the screen.
Am I correct about any of this?
Will Black
“Casinos aren’t built by Winners”.

• Matt Bourie

Now we have asked this question several times to several different slot machine manufactures and they don’t like to answer it. They seem to tip toe around it thinking that if they answer it it will some how cause people to be able to beat their machines. But when asked how many numbers it goes through per second, the best answer I could get was, “a lot.”

But yes, the RNG is running constantly anytime the machine is turned on. There is an interesting story about someone many years ago at a smaller casino that figured out that the casinos turned off the machines at night when they closed and that the RNG’s started to run the exact same cycle when turned on again and won a lot of money before getting caught. I would assume that has been fixed by now.

As for the last part of your question, we did have one slot manufacturer tell us that with their specific machines, the RNG stopped as soon as the button was pressed and that while the reels were spinning the combination was already chosen and that it didn’t matter if the player watched the reels stop naturally or pressed the stop button themselves, the result would be the same. They did say that it was possible other companies did different things but they didn’t know.