How prediction markets work
Published 2026-05-17 · Last reviewed 2026-05-17
TL;DR
- Prediction markets are exchanges where traders buy and sell YES/NO contracts on real-world events.
- A YES share pays $1 if the event happens, $0 if it doesn't. The current price (e.g. 0.32) is the market's implied probability (32%).
- The two venues that matter: Kalshi (CFTC-regulated, US-legal) and Polymarket (on-chain, global).
A prediction market is a stock market for things that haven't happened yet. That's the whole pitch — the rest is mechanics.
What a prediction market actually is
A prediction market is an exchange where two traders agree on a price for a contract that pays $1 if a specific real-world event happens and $0 if it doesn't. The price they agree on — say, 32¢ — is the market's collective answer to the question "what's the probability this happens?"
That's it. The rest is plumbing: how the order book matches buyers and sellers, how the resolution source is verified, how the platform stays legal. The core idea is small.
How prices encode probability
Imagine a contract on "Harvard's acceptance rate falls below 3% this cycle." A YES share pays $1 if true, $0 if false. If you and I agree on 32¢, we're both saying we think the odds are roughly 32%. If new information makes the event more likely, the price moves up; if less likely, down.
Across thousands of trades, this price tends to be more accurate than expert forecasts — because traders with edge keep adjusting it, and the ones who are wrong lose money and trade smaller next time.
Who's trading, and why
Three rough groups: hedgers protecting against an outcome they care about, informed traders with a view sharper than the market, and liquidity providers who just want to earn the spread. Each one improves the market: hedgers add volume, informed traders correct prices, liquidity providers tighten the spread.
How a market settles
At expiration, the platform reads the resolution source. If the answer is YES, all YES shares pay $1 and all NO shares pay $0. Money moves automatically. On Kalshi, this is handled by a CFTC-regulated team; on Polymarket, by the UMA oracle network with a dispute window. Settlement on liquid markets is usually instant; disputed markets can take days.
Where to trade
Two venues cover almost everything:
- Kalshi — CFTC-regulated, legal in most US states, USD deposits. Open a Kalshi account.
- Polymarket — on-chain, deeper market selection, USDC. Geo-blocked in the US. Open a Polymarket account.
That's the whole stack: a contract, a price, a resolution, a venue. Everything else — liquidity, fees, oracles, dispute windows — is the friction between those four things and a smooth experience.
Frequently asked questions
Is a prediction market the same as gambling?
Economically it shares characteristics with betting, but legally Kalshi operates as a CFTC-regulated derivatives exchange. Its contracts are event derivatives, not wagers.
How is the price a probability?
Because each share pays exactly $1 on YES and $0 on NO, the fair price equals the probability of YES. If the market thinks an event is 32% likely, YES should trade near 0.32.
Who decides if YES or NO wins?
Each market lists a resolution source — a press release, official ruling, or specified URL. An oracle reads it and settles. On Kalshi the oracle is Kalshi; on Polymarket it's the UMA network.
Can I lose more than I put in?
No. Maximum loss on any contract is what you paid (max $1 per share). There's no margin, no leverage.
Where should a beginner start?
If you're in the US and want real money, Kalshi. If you want maximum market selection and are outside the US, Polymarket.
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