Polymarket is much more complicated than you expect, because you can make money while making the “wrong” bet. The best way to understand it is to try it out with your friends. Have one person watch the murder mystery, and then create a stack of a few “bets” for each suspect, worth $10, $30, $50, $75, $100. Each of these shares pays the same at the end of the game, say $120, if the suspect is revealed to be the murderer. Give each of your friend $150 in Monopoly money. Players can buy a share at any time from the bank or from each other at any point for any price. The person with the most money at the end wins!

As you play, you’ll notice you can make money by trading bets. Right now, it looks like the butler did it, so if you’re heavily invested in the butler you can sell those shares while they’re high, and buy the tennis coach. Next time the narrative of the movie shifts, you can sell the tennis coach and buy the spouse. You can even win the game without ever successfully guessing whodunnit.

Polymarket is like this. There are propositions, and you can buy shares based on a current price. Based on the price of the shares relative to each other, you can mathematically work out the probability the market believes something has of happening. It’s like gambling, but more complicated, so you’re much less likely to actually make any money off it unless you’re really steeped in economics and markets. Notably, Polymarket arose out of work by economists who proposed it as an alternative to voting that would allow richer people to vote more, and poorer people to vote less.