Where the jackpot money comes from
In a progressive game, a share of every stake is allocated to the jackpot pool. When that prize fund is won, it is paid out of the quoted return percentage. This is why a quoted return that includes a share such as 2 per cent may not seem to add up to the total payback that you experience.
The meter is the visible sign of this: on screen, it looks just like a scale of values. As more players place more stakes, the meter rises. Others may show a growing pile, but the rising meter is the same. Each stake funds the jackpot in the smallest amount — you are contributing yourself as you play.
When the jackpot is won, the prize fund is paid out. But who wins it, and how it is allocated to the jackpot winners, depends on the structure of the game.
Two figures that look like one
The information screen shows whether the quoted return includes the progressive jackpot share. Rather than just a quoted figure, it's worth looking at the information screen for the basis of the return.
The information screen states the basis of the return. But the most visible sign of the share is the meter. If you see that, you won't be making a fair comparison if you match that figure to a return percentage that doesn't include a jackpot share.
Doing the subtraction
Where you can filter down the quoted return like this, you can work out how much of it reaches the jackpot fund, and what that proportion amounts to in percentage points. As an example, if the quoted return is 96 per cent and the jackpot share is 2 percentage points of that, the base return is 94 per cent, as you subtract the share from the total.
So, in this example, in ordinary play, you can expect a base return of 94 per cent, while the total of 96 per cent is what happens when the jackpot is hit. The key difference is that the jackpot share, in this case, 2 per cent, is paid out in a lump sum for one round, rather than spread across the play that hit the jackpot.
Games may differ in their total return quotes and jackpot shares. In other words you won't be able to tell a flat game by its exclusion of a jackpot share or a progressive game by the inclusion of one: it's about quoting the percentage on the same basis, rather than one basis for the base game and the other for the jackpot.
Comparing like with like
It's a flat return if it doesn't fund a prize fund: a game that uses its stakes to pay out on regular outcome and nothing else, rather than to fill up a prize that only some rounds can win. That means you can't get a proper comparison between a progressive game with an including total return quote, and a flat one. Even the 94 per cent example above is only truly comparable to a flat game quoted on the same (base) basis, because the quoted total is not the same thing as the playable (base) return.
Finally, there is the matter of the conditions for claiming for the jackpot to worry about. There are two types of progressive jackpot that might limit the players who can win the prize.
One is the must-drop: this one stipulates that the prize fund must be paid out before a certain level or by a certain date. This is in the game's own information — the game's information states the conditions.
The other one is tied to the stake. You might see a qualifying bet that you need to make in order to be eligible for the top prize, or for any at all. Again, this changes the proportion of players who can claim the share and it is often in the information, where the levels of stake are named and by dollar sign, so here you are looking for the stake level rather than just a dollar sum.
Neither stating all players can claim, nor whether all players want to, is the reason to be clear here.