Methodology
Last reviewed . Laws and platform rules change; check the sources linked below.
Data
We read public market data from Kalshi and Polymarket every two minutes. We track markets with at least $5,000 traded in the last 24 hours, because smaller markets move on very little money. History is kept in 10-minute steps for two days, then one point per hour.
From price to probability
For each yes/no market we use the midpoint between the best bid and best ask when they are within 10¢ of each other. When the spread is wider, we use the last traded price. Polymarket markets with more than two outcomes are not included yet.
Combining venues
When the same question trades on both platforms, and we have checked that the resolution rules match, we show a combined chance weighted by each market’s 24-hour volume. Each venue’s own price is always shown next to it.
What counts as a big move
A move is recorded when the chance changes by at least 8 points within 1 hour or 12 points within 1 day. After a move, we wait 2 hours before recording another one for the same market, so one event is not counted many times.
How explanations are produced
For each big move we look at public news headlines from the few hours before it and rank them by how closely they match the market. An AI model then writes one sentence naming the headline that most likely explains the move. The sentence may not contain numbers, odds or advice; if it breaks those rules, or if the model is unsure, we show the best-matching headline itself, labeled “Moved after”. If nothing matches, we say that no clear news trigger was found. We always link the source.
Explanations are a best effort, made in minutes, and can be wrong. Moves sometimes come from large trades, not news.
Call it
Each day we pick three heavily traded markets. Players call whether each will be higher or lower at 00:00 UTC than at 16:00 UTC, when picks close. Changes under half a point count as flat and void the question. There is no entry fee and no cash prize.
Corrections
See our editorial policy.