Original data studies: thousands of resolved markets, measured to show how prediction markets really perform.
Most Polymarket traders lose: 74% of 10,050 randomly sampled active wallets are down all time. We analysed the top 10,050 traders, the leaderboards for every category and the profiles of 1,645 top wallets: who wins, how concentrated profits are, big bets versus grinders, and what it means for you.
Sports made up 48% of Kalshi’s trading in a 24-hour snapshot and politics 39%, five days before the midterms. On Polymarket’s international site sports and politics were about a quarter each, with geopolitics and crypto close behind. Tennis, golf and college football led Kalshi’s sports volume; soccer and esports led Polymarket’s. The top markets, how concentrated trading is, and what it means.
We pulled every open market on Kalshi and Polymarket and measured the gap between the best bid and ask. Most markets do not trade on a given day; among those that do, the median spread was 2¢ on Kalshi and 2.4¢ on Polymarket, falling to 1¢ in the busiest markets. Spreads by volume, price and category, and how to keep trading costs down.
We matched 351 outcomes listed on both Kalshi and Polymarket across 31 events and compared their prices at the same moment. In liquid markets the median gap was 1 point, Kalshi was cheaper for “Yes” slightly more often, and Republicans were priced higher on Kalshi in 11 of 15 political races. The data, the crossed books and what it means for traders.
We pulled 358,236 resolved markets from Polymarket and Kalshi and checked every price against what happened. Calibration curves, Brier scores by category and time horizon, Polymarket vs Kalshi (including 28 Fed meetings head to head), why ladder markets are overconfident, the favourite-longshot bias, the biggest upsets and the free dataset.
