What Is a Prediction Market? How Event Trading Works

A prediction market is an exchange where traders buy and sell contracts tied to the outcome of a real-world event — an election, a Fed rate decision, a playoff series, a rocket launch. Each contract pays a fixed amount (usually $1) if the event happens and nothing if it doesn't, so the live price doubles as a probability: a YES contract trading at 34 cents means the market is pricing roughly a 34% chance. In short, a prediction market turns "what does the crowd actually believe?" into a number you can watch move in real time — and trade against.

How does a prediction market work?

The core instrument is the binary event contract. A market poses a precise, verifiable question — "Will the Fed cut rates at its September meeting?" — with defined resolution rules and a settlement source. Traders can take either side:

• Buy YES if you think the event is more likely than the current price implies.
• Buy NO (or sell YES) if you think it's less likely.

If the event happens, YES settles at $1 and NO at $0; if it doesn't, the reverse. Between listing and resolution, the price floats freely as traders react to news, data, and each other.

A worked example: say a contract on a rate cut trades at 34¢. A trader who buys 100 YES contracts pays $34. If the cut happens, those contracts settle for $100 — a $66 gain before fees. If it doesn't, the $34 is gone. Crucially, nobody has to hold to resolution: if new inflation data pushes the price from 34¢ to 55¢, the trader can sell immediately and keep the difference. That constant ability to enter and exit is what makes these markets rather than bets.

Why does the price equal a probability?

On one binary contract, complementary YES and NO settlement values total $1 under the venue's written rules. If executable asks sum to less than $1, the entered arithmetic shows a theoretical gross margin. Capturing it is a separate problem: both legs must fill at the displayed size, fees and slippage must fit inside the margin, and the contracts must not be voided or settled on different terms. That relationship helps keep complementary prices near $1 and makes each side legible as an implied probability. For a deeper walkthrough of order books, spreads, fees, and execution limits, see how prediction market odds work.

Why do prediction market prices carry information?

Prediction markets are information-aggregation machines. Three forces do the work:

1. Skin in the game. Unlike a poll respondent, a trader who is wrong loses money. That filters out cheap talk and rewards people who actually know something.
2. Continuous updating. Markets reprice the moment news breaks — often minutes or hours before analysis catches up. Watching how much a price moves on a headline tells you what was already priced in.
3. Diverse, competing views. A price is the standing disagreement between everyone trading it. When new participants with better information arrive, they profit by correcting the price — and the market gets smarter.

This is why economists have studied prediction markets for decades. The Iowa Electronic Markets, an academic project at the University of Iowa running since 1988, became famous for producing election forecasts that compared favorably with major polls across multiple cycles. Justin Wolfers and Eric Zitzewitz's 2004 Journal of Economic Perspectives survey formalized the case for market prices as probability forecasts. The literature is not one-sided — markets have well-documented failure modes — and we walk through the evidence honestly in are prediction markets accurate?

What can you trade on a prediction market?

Modern platforms list far more than elections:

• Politics & elections — presidential and congressional races, legislation, cabinet changes, geopolitical events.
• Economics & rates — Fed decisions, CPI prints, jobs numbers, GDP, recession odds.
• Sports — game and championship outcomes on venues cleared to list them.
• Crypto — coin prices at expiry, ETF decisions, protocol events; see our guide to crypto prediction markets.
• Culture & entertainment — awards, box office, streaming numbers.
• Weather & science — temperature records, hurricane landfalls, launch windows.

Every market has resolution criteria worth reading before trading — the difference between "announced" and "takes effect," or which data source settles the question, decides who gets paid. W.E.T. shows venue-attributed listings together but publishes a numerical cross-venue comparison only after confirming that the contracts describe the same outcome and compatible settlement basis. Explore that event-first map on the W.E.T. event dashboard.

Who runs prediction markets?

Two venues anchor the space today:

• Kalshi — a CFTC-regulated designated contract market based in the US. Accounts are funded in dollars, contracts are legally regulated derivatives, and US residents can trade directly.
• Polymarket — the crypto-native venue, settled in USDC on the Polygon network. It historically served non-US users and moved toward regulated US access after acquiring a CFTC-licensed exchange in 2025.

Beyond the big two: Interactive Brokers offers regulated event contracts, Manifold runs a play-money market, Metaculus aggregates forecasts without trading, and PredictIt operated for years as an academic project under a CFTC no-action letter. We compare all of them in best prediction market platforms, and go head-to-head on the leaders in Kalshi vs Polymarket.

Are prediction markets legal?

In the US, yes — on regulated venues. Event contracts on a CFTC-designated exchange like Kalshi are legal derivatives, the same regulatory family as futures. The boundary questions (which contract types are permitted, state-level treatment of sports markets) are still being worked out between regulators, courts, and the exchanges, and coverage evolves as rulings land. Elsewhere, access depends on local law and each platform's own geo-restrictions. None of this is legal advice: check the platform's terms for your jurisdiction before funding an account. Our FAQ covers the common questions.

How is a prediction market different from a poll or a sportsbook?

Versus a poll: a poll measures stated opinion at a moment in time; a market measures committed capital continuously. Polls sample; markets aggregate. When they disagree, the interesting question is why — sometimes the market knows something, sometimes thin liquidity is telling you nothing at all.

Versus a sportsbook: a bookmaker sets the line and takes the other side of your bet, building its margin into the odds. A prediction market matches traders against each other on an exchange order book — the venue takes fees, not positions. That structure usually means tighter implied pricing and, more importantly, the ability to exit mid-event instead of riding a ticket to the final whistle.

How do traders actually use prediction markets?

Three broad modes show up across the live events we track:

1. Forecast consumers watch prices as a probability dashboard — journalists, analysts, and anyone who wants a number instead of a narrative.
2. Event traders trade the news cycle: taking positions ahead of catalysts (a debate, a data print, a court ruling) and exiting into the repricing. Our news wire exists to connect headlines to the markets they move.
3. Hedgers offset real-world exposure — a business exposed to a rate decision or an election outcome can take the other side in the market.

If you're exploring the trading side, start with the frameworks in prediction market trading strategies before putting real money at risk — position sizing and fee awareness matter more than any single forecast.

Where to go next

The fastest way to understand prediction markets is to watch them react to a live catalyst. The W.E.T. event dashboard organizes this week's market-moving events with live odds from Kalshi and Polymarket side by side, and the community is where traders argue about what's priced in before the market decides who was right.