Methodology
How TPM compares prediction-market prices
A price comparison is only useful if the two markets really ask the same question, settle the same way, and the prices are current. This page explains the rules TPM applies to each of those, in plain language. It was last reviewed on October 21, 2026.
1. Matching markets across venues
Kalshi and Polymarket list many of the same questions, but word them differently. Most of each catalog is generated from templates, such as one market per state for a Senate race. TPM reads each question into its parts: the kind of question, the office or topic, the place, the year and any variant. Markets whose parts are identical on both venues are grouped as the same question before any fuzzy text comparison runs.
The year comes from the question itself (its title, subtitle or series), never from when a market happens to close. Questions that do not follow a template are compared on their full text and rules. Where a match is ambiguous it is held for review rather than shown. An automated reviewer can confirm that two markets ask the same question, but it can never certify that they settle identically; that needs the rule check below.
Inside a matched question, each answer is lined up by what actually decides the payout, not by its label: the party for most election races, the person for nominee and presidential markets, exact number ranges for seat counts and price ladders. Placeholder answers such as “Person A” or “Other” are never linked.
2. Settlement-parity checks
Two markets can ask the same question and still pay out differently, for example if one settles on a certified result and the other on a news call, or treats an independent candidate differently. For each kind of question TPM compares the venues’ written rules once and records the result:
| Label | Meaning |
|---|---|
| Full parity | The rules produce the same payout in every case we can identify. |
| Partial parity | Same payout in all ordinary outcomes; the specific edge cases that differ are listed alongside any price comparison. |
| No parity | The markets are related but settle differently. They may be shown together for context, never as a price gap. |
A range on one venue that equals the sum of several ranges on the other is treated as a derived relation, not a direct match, and is not shown as an opportunity.
3. Price gaps
A price gap is the edge you could actually trade at the top of each order book: buy Yes at the best ask on one venue and sell Yes (or buy No) at the best bid on the other. TPM calculates gap = best bid on venue B − best ask on venue A and takes the better of the two directions. It never uses last-traded prices, because those can differ widely while the order books overlap.
- A side priced at 0 or 1, or a crossed book on one venue, counts as no quote. Without a usable quote on both venues there is no gap.
- Gaps are gross: venue fees, slippage and depth beyond the best price are not yet deducted.
- Where no tradable pair exists, a page may show the difference in displayed prices, labeled “price gap · not executable”.
4. Freshness
TPM receives live order-book updates from each venue’s streaming feed and also polls each venue on a schedule. Every price carries its age, and stale numbers are dimmed or withheld rather than shown as if current.
Live quotes
| State | Rule | What you see |
|---|---|---|
| Live | Updated less than 15 seconds ago, or the venue feed is healthy and confirms a quiet book | Shown as is |
| Delayed | 15 to 60 seconds old, or the feed is slow | Dimmed, “Delayed quote, recheck” |
| Stale | 60 seconds or older, or the feed is down | Bid, ask and gap withheld; last price marked “last known” |
Price gaps from polled prices
| State | Age of the older side | What you see |
|---|---|---|
| Actionable | Under 10 minutes | Normal; the only state that may be called arbitrage |
| Indicative | 10 minutes to 2 hours | Dimmed, “indicative · N min old” |
| Stale | 2 hours or more, or no timestamp | Gap withheld, trade links hidden |
Feed health for each venue is public on the status page.
5. Known limits
- Coverage is Kalshi and Polymarket today. Not every market has a counterpart on the other venue.
- Gaps do not include fees, slippage or order-book depth.
- Settlement checks are made per kind of question from the venues’ published rules, which can change.
- Nothing on TPM is financial advice. Always read a venue’s own rules before trading.
Found a mismatch or a wrong label? Email [email protected] and we will review it.