What Are Prediction Markets?

In June 2026, a Kalshi contract on which party wins the Senate was trading YES on Republicans at $0.58 and YES on Democrats at $0.42. Polymarket had it at $0.58/$0.43 the same week. Neither number is a payout table set by a bookmaker — it's the price traders are willing to pay right now, and that price is the market's live estimate that the event happens. That's the whole idea behind prediction markets: turn a forecast into something you can buy, sell, and watch move in real time.

The Mechanism: Price Is Probability

A prediction market lists a contract tied to a specific, verifiable outcome — "Will the Fed cut rates in September?" or "Will the Democrats win the House?" Traders buy YES or NO shares against each other. On Polymarket, shares trade between $0.00 and $1.00; on Kalshi, between $0.01 and $0.99, with YES + NO always summing to exactly $1.00. Whichever side wins, that share redeems for $1. The losing side redeems for $0.

That structure makes the price mathematically equivalent to a probability. A contract sitting at $0.70 means the market, in aggregate, is pricing roughly a 70% chance of that outcome. Move a large order through the book and you move that implied probability — which is exactly how traders read sentiment shifting on a debate night or a jobs report.

Under the hood the two largest venues get there differently. Polymarket runs a hybrid central limit order book (CLOB) — off-chain matching, on-chain settlement through a Conditional Token Framework (CTF, ERC-1155) on Polygon, collateralized in USDC. Kalshi is a CFTC-regulated Designated Contract Market (DCM) — KalshiEX LLC handles trading, Kalshi Klear LLC clears and custodies funds at a federally regulated clearinghouse. Different plumbing, same core mechanic: price equals probability.

How Prediction Markets Aggregate Information

The reason these prices tend to be informative isn't magic — it's incentive. Anyone who thinks the market is mispriced can trade against it and get paid if they're right. A trader with inside knowledge of a company's earnings, a pollster with a fresh internal, or someone who just watched a debate closely all have a financial reason to push the price toward what they believe is true. Thousands of those individually-motivated trades get compressed into one number: the last traded price.

This is different from a poll, which asks people what they think or who they'll vote for, and different from a pundit's forecast, which carries no financial cost for being wrong. A prediction market participant loses real money for being wrong and gets paid for being right — that's the filter that (in theory) makes the aggregate more honest than a survey of stated opinion.

Resolution matters just as much as pricing. Polymarket settles disputed outcomes through the UMA Optimistic Oracle: anyone can propose a result and post a USDC bond (around $750 for a standard question, $5,000+ for high-value markets); if unchallenged it settles in hours, if disputed it escalates to a UMA token-holder vote over 4–7 days. Kalshi resolves internally against sourced data as a regulated exchange. Both approaches exist to answer the same question: who decides what actually happened, and how do you stop someone from gaming that decision.

The Major Venues in 2026

Four platforms dominate discussion of prediction markets right now, and they're not interchangeable:

Venue	Structure	Scope	US legal status
Polymarket	Peer-to-peer exchange, Polygon/USDC, UMA oracle resolution	Politics, crypto, sports, culture, world events — very broad	Regulated US exchange live since Dec 2, 2025 (via QCEX); offshore exchange geoblocked to US users
Kalshi	CFTC-regulated DCM, USD settlement	Broad, with particular depth in economics, weather, and Fed contracts	Legal in all 50 states as a federal DCM since 2020; some state friction on sports contracts
PredictIt	CFTC no-action framework, academic-run	Political-event contracts only, narrow scope	Legal under no-action letter; per-position cap now up to $3,500
Iowa Electronic Markets (IEM)	Academic exchange, Univ. of Iowa, CFTC no-action since 1988	Mostly US elections, small research-scale positions	Legal, non-commercial, education/research focused

Polymarket and Kalshi carry the overwhelming majority of volume and the deepest order books; PredictIt and IEM are smaller and narrower but have decades of academic track record behind them. For a full side-by-side on fees and mechanics, see how the best prediction market platforms compare in 2026. If you're focused on one venue, Polymarket-specific trading strategies and the full Kalshi trading guide go deeper into each platform's mechanics and order types.

How Accurate Are They?

This is where prediction markets earn their reputation. A widely-cited study by Berg, Nelson, and Rietz tracked the Iowa Electronic Markets against 964 individual polls across five US presidential elections from 1988 to 2004 and found IEM prices beat the polls' predictive accuracy 74% of the time. More recently, reported figures put Polymarket ahead of traditional polling in roughly 73% of 2024–2025 elections, with an average Brier score (a standard accuracy measure where lower is better) around 0.15–0.18 versus 0.22–0.25 for polls — treat that second figure as a secondary-sourced estimate rather than an audited number.

Calibration research backs this up at a granular level: contracts priced around 70% tend to resolve YES roughly 68–72% of the time, and markets are most accurate at the extremes — contracts priced in the 90–100% range. The key distinction to keep in mind: a poll measures what people say they'll do, a prediction market measures what people are willing to bet will happen, backed by money. Those are different instruments, and they don't always agree. For the deeper dive on this, including where markets get it wrong, see how accurate prediction markets really are.

What You Actually Trade

Once you understand price-as-probability, everything else is strategy. Some traders buy and hold a view through resolution — a straightforward directional bet that Trump's approval rating (38.8% as of June 24, 2026) moves a certain way, or that a Fed decision lands where they expect. Others trade the spread between venues, since Polymarket and Kalshi don't always price the same event identically — that's the basis for cross-venue prediction market arbitrage. Others post resting limit orders and get paid the spread, functioning more like a market maker than a directional bettor.

With the 2026 US midterms landing November 3 and over 500 active midterm markets live across Kalshi and Polymarket alone, this is a busy year to be watching these prices move. If you want the practical playbook — not just the mechanics — venue-agnostic prediction market strategies covers seven approaches that work across any exchange.

Watching one venue's order book is fine for casual reading. Trading across venues in size is a different job — you need live depth, fee math baked in per market, and a way to catch mispricing before it closes. That's the gap PolyMarketMaker is built to fill: a desktop terminal with order-book ladders, depth charts, a predictive arbitrage scanner across Polymarket US, Polymarket global, Kalshi, and PredictIt, and backtesting so you can test a read before risking capital. Simulation runs $149/mo, Live Trading $299/mo.

FAQ

What are prediction markets and how do they work?

A prediction market lets traders buy and sell shares tied to the outcome of a real-world event. A YES share pays $1 if the event happens and $0 if it doesn't; a NO share does the opposite. The live share price is the market's running estimate of that event's probability.

How is a prediction market different from a sportsbook or the stock market?

A sportsbook sets odds and takes the other side at a fixed vig. A prediction market is peer-to-peer: prices move only from trader-to-trader orders, there's no house, and contracts settle to a fixed $1/$0 on a defined event rather than tracking an ongoing asset price.

Which prediction market platforms are the biggest in 2026?

Polymarket and Kalshi carry the most volume and breadth. PredictIt is narrower, limited to political contracts under a CFTC no-action framework. IEM is the oldest, running as an academic no-action market since 1988.

Are prediction markets accurate?

The Iowa Electronic Markets beat 964 individual polls in accuracy 74% of the time across five US presidential elections from 1988–2004. Reported figures show Polymarket ahead of polling in roughly 73% of 2024–2025 elections, though markets and polls measure different things.

Are prediction markets legal in the US?

Kalshi has operated as a CFTC-regulated exchange since 2020. Polymarket relaunched a regulated US exchange on December 2, 2025. PredictIt runs under a CFTC no-action letter for political contracts. State rules still vary — check your state.

This article is for educational purposes only and is not financial advice. Trading involves risk of loss.