What Are Prediction Markets? A Plain-English Guide to Event Contracts

A prediction market is an exchange where you buy and sell contracts on whether a specific real-world event will happen. Each contract settles at $1 if the event occurs and $0 if it does not, so the price is a probability in dollars: a contract trading at 62 cents is the market saying, collectively, that there is roughly a 62 percent chance. In the US these are called event contracts, and the venues that list them are regulated federally by the Commodity Futures Trading Commission rather than by state gambling boards.

That one structural fact drives everything else on this page. You are not betting against a house that sets a line; you are trading with other people at a price the order book sets, the venue charges an explicit fee instead of shading the odds, and you can usually sell your position before the event resolves. Here is how the whole thing works, in plain English, for someone who has never placed a trade.

How an Event Contract Actually Works

Every market starts as a question with a hard edge: will this team win, will the Fed cut rates at the September meeting, will this film gross more than a stated number by a stated date. The venue publishes the resolution source and the deadline up front, because the contract is only tradable if everyone can agree afterward what happened.

You take a side by buying yes shares or no shares. Prices for the two sides sum to roughly $1, since exactly one of them will be worth a dollar at the end. Buy 100 yes shares at 40 cents and you have put up $40, with $100 coming back if the event happens and nothing if it does not.

When the deadline arrives, the venue resolves the market against its named source, winning shares pay out at $1, losing shares expire worthless, and the cash lands in your account balance. Our guide to how event-contract settlement works covers resolution sources, disputed outcomes, and payout timing in detail, and the step-by-step trading guide walks through order types and reading an order book.

Why the Price Is the Probability

This is the idea that makes prediction markets interesting to people who do not otherwise gamble. Because a contract pays exactly $1 when it hits, the price someone will pay today is a direct statement about how likely they think it is. At 25 cents, buyers are accepting a 4-to-1 payout, which only makes sense if they believe the chance is better than one in four.

Aggregate thousands of those decisions, all made with real money at stake, and the price becomes a live probability estimate that updates the moment anyone disagrees enough to trade. That is the wisdom-of-crowds claim in one sentence, and it is why journalists now quote these prices alongside polls.

• A price is not a promise. An 80-cent contract loses one time in five when the market is well calibrated. That is the design working, not failing.
• Thin markets lie more. A price nobody is trading against is one person’s opinion, not a crowd’s estimate.
• The number is the market’s, not ours. Anywhere this site quotes an implied probability, it is what the venue’s prices say, attributed and dated, never our forecast.

Where the Price Comes From

There is no oddsmaker in this picture. A market’s price is simply the highest someone is currently willing to pay meeting the lowest someone is willing to accept, listed together in an order book. When those two numbers touch, a trade happens and the price updates.

The gap between them is the spread, and it is the hidden cost of trading a quiet market. On a heavily traded contract the spread might be a cent, so getting in and out costs almost nothing beyond fees. On a market nobody is watching it can be ten cents wide, which means you lose a tenth of the contract’s value the moment you buy and sell.

This is why liquidity gets discussed so much in prediction-market circles. Deep markets are not just more interesting, they are cheaper to be wrong in, and they produce prices that mean something because many people are pushing on them.

Who Trades These, and Why They Exist

The trading population is a mix. Some participants are there for the same reason people bet on sports: they have an opinion and want action on it. Others are hedging something real, which is the use case the instruments were designed around. A business exposed to bad weather, an interest-rate decision, or an election outcome can offset part of that exposure by taking the other side on an exchange.

That hedging function is why the CFTC regulates these contracts as derivatives rather than treating them as games, and it is the reason the legal fight described elsewhere in this section is genuinely hard rather than obviously resolvable. The same contract can be a hedge for one participant and a wager for another, and the instrument does not know the difference.

What Can You Trade On?

Anything with a clear, checkable resolution. The categories that carry real volume are politics and elections, economics (rate decisions, inflation prints, jobs numbers), sports outcomes, weather and climate readings, entertainment and awards, and company or technology milestones.

Sports is the category to understand carefully, because it is the one under legal pressure. Several states have moved specifically against sports event contracts while leaving the rest of the board alone, so the menu you see can differ from the menu someone in another state sees. Our state-by-state legality guide tracks exactly who has done what, with dates and sources.

How Prediction Markets Differ From Sportsbooks

Four differences matter in practice, and they all follow from trading against people instead of a house.

Which model is better for the person holding the position is a genuine question rather than a marketing one, and we treat it that way in our piece on whether prediction markets are safer than sportsbooks. Short version: they are differently risky, and the honest comparison depends on which risks you personally carry.

How They Differ From Stocks and Options

Event contracts look like financial instruments and are regulated like them, but they behave differently from anything in a brokerage account. A share of stock has no expiry and no ceiling; an event contract has both. It converges to either $1 or $0 on a known date, which caps your upside per contract and makes time a hard constraint rather than a soft one.

The closest familiar cousin is a binary option, and the practical consequence is that you cannot ride out a bad position the way an investor waits for a stock to recover. When the market resolves, it is over. Treat the money at risk accordingly.

The Risks Worth Naming

Prediction markets are marketed as smarter than gambling. The mechanics really are different, but the money at risk behaves the same way, and these are the risks we would want a friend to hear before their first trade.

• You can lose the whole stake. A losing contract expires at zero. There is no partial credit for being nearly right.
• Fees are small but not zero, and they bite hardest on the coin-flip markets people trade most. See what a trade actually costs for the formulas.
• Thin markets are expensive to leave. A wide spread means your exit price is worse than the last quoted price.
• Information asymmetry is real. Some counterparties know more than you, and federal regulators have been actively scrutinizing insider trading in event markets.
• Access can change under you. Court orders have already removed sports contracts from several states with little notice.
• The tax treatment is unsettled. Gains are taxable, but how they are classified is still an open question. Our tax explainer covers what is and is not decided.

The Vocabulary, Decoded

Six terms cover most of what you will read on a trading screen:

• Event contract: the instrument itself, a yes/no claim that settles at $1 or $0.
• Yes / no shares: the two sides of a market. Buying no is a position in its own right, not just declining to buy yes.
• Order book: the live list of what people will pay and accept. The gap between the best of each is the spread.
• Maker and taker: a maker posts a price and waits, a taker accepts a price already on the book. Venues charge them differently, and one venue pays makers.
• Settlement: resolving the market against its stated source and paying out.
• Implied probability: the price read as a percentage, which is the whole point of the design.

Once those six make sense, everything else on a prediction-market screen is just a variation on them.

If You Decide to Try It

Three habits separate people who learn something from people who just donate to better-informed traders.

1. Read the market rules before the price. The resolution source and deadline define what you are actually buying. Assuming the spirit of a question rather than its letter is the classic beginner loss.
2. Start where the crowd is. A liquid market has a tight spread and a price that reflects real information. A quiet one costs more to enter and tells you less.
3. Size it as entertainment, not income. Even a well-judged 70-cent position loses three times in ten. If a full loss would matter to your month, the position is too big.

And know the boring parts before you need them: what the venue charges, where it operates, and how your gains get taxed. Those three questions have their own guides in this section, linked throughout this page.

Prediction Markets FAQ

The questions people actually ask before their first trade.