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 9:03 PM ET, Sep 28 · 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 113 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.
Last 9 build days
Today's widest disagreements
| Matched event | Kalshi YES | Polymarket YES | Gap |
|---|---|---|---|
| J.D. Vance: 2028 Republican presidential nominee Kalshi vs Polymarket | 44¢ | 50¢ | 6.3pp |
| Alexandria Ocasio-Cortez: 2028 Democratic presidential nominee Kalshi vs Polymarket | 14¢ | 18¢ | 4.0pp |
| Marco Rubio: 2028 Republican presidential nominee Kalshi vs Polymarket | 19¢ | 15¢ | 4.0pp |
| Chicago Bears: NFC North Division Winner Kalshi vs Polymarket | 14¢ | 18¢ | 4.0pp |
| New York Knicks: 2027 Pro Basketball Champion Kalshi vs Polymarket | 8¢ | 12¢ | 4.0pp |
| Alexia Putellas: Women's Ballon d'Or Winner 2026 Kalshi vs Polymarket | 88¢ | 92¢ | 4.0pp |
| Gavin Newsom: 2028 Democratic presidential nominee Kalshi vs Polymarket | 13¢ | 17¢ | 3.6pp |
| Miami Heat: 2027 Pro Basketball Champion Kalshi vs Polymarket | 6¢ | 3¢ | 3.5pp |
| Marine Le Pen: Next French presidential election winner Kalshi vs Polymarket | 43¢ | 39¢ | 3.5pp |
| Anabell Ávalos Zempoalteca: Tlaxcala Governor winner Kalshi vs Polymarket | 0¢ | 3¢ | 3.0pp |
| Jean-Luc Mélenchon: Next French presidential election winner Kalshi vs Polymarket | 13¢ | 15¢ | 2.5pp |
| ACM Neto: Bahia Governor winner Kalshi vs Polymarket | 51¢ | 48¢ | 2.5pp |
| Harry Kane: Who will win the Ballon d'Or in 2026 Kalshi vs Polymarket | 44¢ | 42¢ | 2.3pp |
| Liverpool: English Premier League Champion Kalshi vs Polymarket | 8¢ | 6¢ | 2.0pp |
| Chiang Wan-an: Taipei mayoral election winner Kalshi vs Polymarket | 80¢ | 82¢ | 2.0pp |
| Jerônimo Rodrigues: Bahia Governor winner Kalshi vs Polymarket | 46¢ | 48¢ | 2.0pp |
| Tampa Bay Rays: Pro Baseball Champion Kalshi vs Polymarket | 9¢ | 11¢ | 1.9pp |
| San Francisco 49ers: 2027 Pro Football Champion Kalshi vs Polymarket | 10¢ | 8¢ | 1.8pp |
| Jordan Bardella: Next French presidential election winner Kalshi vs Polymarket | 3¢ | 1¢ | 1.7pp |
| Kostadin Kostadinov: Bulgarian presidential election winner Kalshi vs Polymarket | 2¢ | 0¢ | 1.7pp |
| Mark Kelly: 2028 Democratic presidential nominee Kalshi vs Polymarket | 4¢ | 2¢ | 1.6pp |
| François Hollande: Next French presidential election winner Kalshi vs Polymarket | 6¢ | 5¢ | 1.4pp |
| James Talarico: 2028 Democratic presidential nominee Kalshi vs Polymarket | 3¢ | 2¢ | 1.3pp |
| Dominique de Villepin: Next French presidential election winner Kalshi vs Polymarket | 1¢ | 0¢ | 1.3pp |
| Xavier Becerra: California Governor winner Kalshi vs Polymarket | 96¢ | 95¢ | 1.2pp |
Methodology
1. A pair counts only when we can check that both exchanges are asking the same question. Polymarket has to ask whether a named person or team will win a named contest, and Kalshi has to list a who-wins event for that contest and year with exactly one open market carrying that name. Pairs with a bid and ask more than 10 cents apart, contests ending within three days, and midpoint gaps over 25 points are dropped. The full rules are on the cross-listed pairs page.
2. For each pair we take the absolute difference between the two midpoints (halfway between bid and ask), in points. Pairs that agree stay in the average, so the index reads low when the exchanges agree.
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-listed pairs and the biggest price moves.