How the category got this big
A prediction market is a real-money market on a yes/no question, and for years the category was a niche. That changed fast. By mid-July 2026 Kalshi and Polymarket had together crossed roughly $150B in cumulative trading volume, and in June the major platforms combined topped $50B in a single month for the first time — a ~75% jump from May (CoinDesk, cited above). The engine of that spike was sport: the 2026 FIFA World Cup, widely described as the biggest gambling event in history.
The World Cup spike
Kalshi alone recorded more than $31B in notional volume in June (up ~70% from May), with its World Cup markets accounting for about $7.4Bof that — more than its entire March Madness figure — before the group rounds were even complete. Polymarket's international platform hit a record $10.8B, and its regulated US platform did about $3.5B. You can watch the live winner-market probabilities that sit under those volumes on Monitoring's World Cup tracker — the final is Sunday 19 July.
The regulatory story
Scale brought scrutiny. US regulators are weighing whether event-contract prediction markets belong inside products built for fund investors, which has delayed planned prediction-market (event-contract) ETFs, while several jurisdictions have moved to block or restrict access. This is public regulatory context, not a verdict: Monitoring reports what is happening, and this page is information, not legal or investment advice. For the detail — the CFTC-versus-states jurisdiction fight and the state-by-state status — see is Polymarket & Kalshi legal.