What bet you can make consistently gives you at least 51% odds? As far as I know, the best you can do in a casino is 48%. If I plug 48% into the simulation, it states there is no Kelly edge for that bet.

Bets with a positive edge can be found most commonly via sports betting, poker games, and the stock market. Although note that most bets you can find via such methods do not have a positive edge, and the edge is not labelled.

More generally, look for any area where bets can be made, and professionals exist who make their living winning such bets. There are professional poker players and sports gamblers; there are not professional roulette players.

As far as casino games, you might find yourself in this situation with a half-decent poker hand or if you're counting cards in blackjack. Casinos don't hand out advantages over the house, which is why the former is coming from other players and the latter is against the rules. As the sibling comment notes, it is generally irrational to participate in casino games and the simulator is correct to tell you not to do so.

This comes up more when you have (or at least believe you have) information that the counterparty doesn't have.

The first time I ran across Kelly it was WRT card counting. There is some rare positive off the top video poker out there.

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