The Divergence Index
One number for how far Kalshi and Polymarket disagree right now: the volume-weighted average gap between YES prices on the same real-world event, measured across every matched cross-venue pair we track.
Updated 5:13 PM ET, Aug 14 · prices refresh four times daily
How to read it. A YES contract priced at 62¢ on Kalshi and 55¢ on Polymarket is a 7-point disagreement about the same future. The index averages those gaps across all 1 matched pairs, weighted by traded volume so a thin novelty market cannot move the number.
Near 0, the venues agree and prices are probably efficient. When the index climbs, one venue is being slow, one crowd is wrong, or news is landing unevenly: either way, that is where the interesting prices live. The pairs driving today's number are listed below, largest gap first.
Today's widest disagreements
| Matched event | Kalshi YES | Polymarket YES | Gap |
|---|---|---|---|
| Ethereum price at Aug 15, 2026 at 5pm EDT: $2,610 or above vs Will the price of Ethereum be above $1,800 on August 16? | 1¢ | 98¢ | 98.0pp |
Methodology
1. Every tracked Kalshi market is matched against every tracked Polymarket market by title token overlap (Jaccard similarity over meaningful words, stopwords stripped, small bonus for a shared category). Pairs below a 0.45 similarity floor are discarded, and matching is one-to-one (each market pairs at most once, best match wins), so only markets confidently about the same event are compared.
2. For each matched pair we take the absolute difference between YES prices, in points. Pairs with a gap under 2 points are treated as agreement and excluded.
3. The index is the volume-weighted mean of those gaps, where each pair's weight is the combined traded volume of both markets. It is recomputed at every site build from the same live data that powers the markets table, and the daily closing value is archived to build the history above.
The index is a measurement, not advice. A wide gap can be a real mispricing, a difference in contract wording, or a settlement-rule mismatch; read both contracts before trading either side. See also cross-venue arbitrage and model mispricings.