A study of 72.1 million trades on Kalshi reveals a systematic wealth transfer from impulsive takers to patient makers. The analysis quantifies a persistent longshot bias, where low-probability contracts win less than their implied odds, creating an Optimism Tax. This effect is strongest in high-engagement categories like Sports, while Finance markets approach efficiency.

Unlike equities, prediction markets are zero-sum. A legal victory in 2024 allowed Kalshi to list political contracts, triggering explosive growth. The platform's 2025 sports markets now dominate trading. The study's methodology assigns each trade to a liquidity taker or maker, calculating returns based on cost basis and resolution outcomes from a dataset of 7.68 million markets.

The core finding is that Makers consistently earn positive excess returns, while Takers lose 1.12% on average. This gap suggests market efficiency relies more on harvesting error than on rational price discovery. The asymmetry is most extreme at 1-cent contracts, where takers win only 0.43% of the time versus a 1% implied probability.