Why prediction market prices differ between platforms
Overview
A prediction market price is the market's estimate of how likely an outcome is, expressed as a share price between $0 and $1. When two platforms list what looks like the same question, those prices often disagree. Some of that disagreement is genuine information; a lot of it is structural.
Price-gap casebook: comparable prices versus false signals
These are illustrative worked examples, not recorded trades, current quotes, or a verified historical archive. The numbers explain the checks; they are not prices observed on Polymarket or Kalshi. A historical case needs dated source quotes, both contract links and settlement evidence before we can publish it as an observation.
| Case | Evidence | What the gap means |
|---|---|---|
| Comparable buy quotes | Same outcome, threshold, observation time and settlement source; buy quotes 62¢ and 57¢ observed together. | 5 percentage points of gross price difference. Fees, depth and execution still need checking; no guaranteed profit. |
| Midpoint versus buy price | A 57¢ midpoint has a 54¢ bid and 60¢ ask; the other platform's buy price is 62¢. | The buy-price difference is 2 points, not 5. A midpoint is not an offer to sell to you. |
| Different thresholds | One contract asks above $100,000; the other asks above $105,000 at the same time. | Different payout conditions. Do not publish the apparent difference as a like-for-like gap. |
| Touch versus closing price | One contract pays if a level is touched at any time; the other checks the closing price on a specified day. | Related topic, different event. Either can win while the other loses. |
| Stale second leg | One quote is 2 minutes old; the other is 12 minutes old. | The comparison is STALE under PP's older-leg rule, not a current trading opportunity. |
| Missing buy quote | One platform has no supported executable buy quote. | Unavailable is not zero. There is no supported two-platform price gap. |
What a price gap actually is
If a contract trades at 62c on one venue and 57c on another, the gap is 5 cents, or roughly 5 percentage points of implied probability. That number only means something if both contracts settle on exactly the same event, at the same time, under the same rules.
Prediction Pantheon checks market identity before comparing source buy prices. Related wording is not enough: different settlement rules or missing evidence can make a price comparison unsafe. A visible gap is not a guaranteed fill or profit.
Why the same question trades at two prices
- Different resolution rules. Two markets can ask the same question in plain English and still settle on different sources, cut-off times, or edge cases.
- Different deadlines. A market that resolves on 31 December is not the same as one resolving on 15 January, even for the same event.
- Different user bases. Polymarket and Kalshi serve different regions and different trader profiles, so sentiment and information can genuinely diverge.
- Liquidity and spread. A thin market's mid-price can sit several cents away from where a real trade would fill.
- Fees and funding costs. Deposit, trading, and withdrawal costs eat into any apparent edge, and they differ by platform and funding method.
- Stale data. Prices update on a pipeline cadence, so a gap can reflect a lag rather than a live disagreement.
How to tell a real gap from a false one
- Open both markets on the source platforms and read the resolution criteria in full.
- Check that the settlement dates match, not just the question wording.
- Look at volume and order book depth on both sides — a gap on a market with almost no volume is usually noise.
- Subtract the round-trip costs: deposit, trading fee, withdrawal, and any currency conversion.
- Re-check the prices at the moment you would trade, not the cached ones you first saw.
If the gap survives all five checks it is worth investigating. Most do not.
Frequently asked questions
Does a price gap mean one platform is wrong?
No. Both prices can be reasonable if the contracts settle differently, if the deadlines differ, or if the two venues have different participants. A gap is a prompt to read the rules, not proof of a mispricing.
How large does a price gap need to be to matter?
It depends entirely on costs and liquidity. A 2-cent gap is usually consumed by fees and spread. Larger gaps often signal that the two markets are not actually equivalent.
How current are the prices on Prediction Pantheon?
Prices refresh on a short pipeline cadence and each market page shows when it was last updated. Always confirm the live price on the platform before trading.