What does 67¢ mean on a prediction market?

It means the market is pricing a ~67% probability that the event will resolve YES. A YES share pays exactly $1 if YES happens; buying it at 67¢ implies you agree the chance is at least 67%.

The spread is the gap between the best buy price (bid) and best sell price (ask). A YES quoted 66¢ bid / 68¢ ask has a 2¢ spread. Tighter spreads mean more liquid, more efficient markets.

Slippage is the difference between the price you see and the price you actually fill at, especially on larger orders. In an AMM, as you buy more YES, the price moves up the bonding curve; the average price on your order is higher than the starting price.

Guides · Mechanics

Reading market prices

Prediction-market prices look simple — just a number from 0¢ to 100¢. The number packs in a lot of information. Here's how to read it.

Price = implied probability

A YES share pays $1 if the market resolves YES and $0 otherwise. If YES is trading at 67¢, the expected value of a YES share equals the price only when the probability of YES is 67%.

Formally: EV(YES share) = P(YES) × $1 + (1 − P(YES)) × $0 = P(YES). Market price ≈ market-implied probability.

YES + NO should sum to ~$1

Because exactly one of YES or NO will be true, a YES share plus a NO share for the same market together pay exactly $1. So the prices should sum to roughly $1.

If YES is 67¢, NO should be ~33¢. If you ever see YES at 67¢ and NO at 30¢ simultaneously, that's an arbitrage — buy both sides for 97¢ and collect $1 on resolution. In practice, automated traders close these gaps in seconds.

Bid, ask, and spread

Bid. The highest price someone is currently willing to pay for a YES share.
Ask. The lowest price someone is currently willing to sell a YES share for.
Spread. Ask − Bid. Tight spreads (1–2¢) signal active, liquid markets. Wide spreads (10¢+) signal thin liquidity.

On Desipoly's launch AMM, "bid" and "ask" are derived from the fixed-product curve rather than a discrete order book — but the concept carries over.

Liquidity and depth

Liquidity is how much you can trade without moving the price. "Depth" describes the shape of liquidity at different prices.

A market with $50k of liquidity can absorb a $500 trade with negligible slippage.
That same market gets a noticeably worse average fill on a $10k trade.
A market with only $2k of liquidity will see a $500 trade move the price several cents.

Slippage, concretely

Slippage is the gap between the quoted price when you start an order and the price you actually pay on average.

Example: YES is quoted at 50¢. You try to buy $5,000 of YES. In a fixed-product AMM, as you buy, the price rises. Your average fill might be 53¢, even though the starting quote was 50¢. The extra 3¢ on every share is your slippage cost.

To reduce slippage: trade smaller, or split large orders, or wait for more liquidity. The Desipoly UI shows estimated slippage before you confirm. Details in LMSR and AMM explained.

Fees

Trading fee. A small percentage of each trade in USDC, kept inside the AMM pool as protocol revenue.
Gas. A few cents of MATIC per on-chain transaction on Polygon.
Resolution bond. Paid by the proposer/disputer — not by regular traders.

How to judge whether a price is "right"

The honest answer: most of the time, you can't. The market's price is the aggregate forecast of everyone who has traded — typically smarter than any one participant.

Trade only when you have an actual information or analytical edge — something you know or can work out that most traders don't. Otherwise, you're paying spread for entertainment.

Common price misreadings

"90¢ means it's a lock." It means a 90% probability — a 1-in-10 upset still happens sometimes.
"3¢ is free money." It means a 3% probability. The event rarely happens but cannot be assumed impossible.
"YES moved from 50¢ to 55¢, the odds improved 10%." No — absolute odds improved 5 percentage points (from 50% to 55%).