I've got every Kalshi World Cup trade in a database. Here is the analysis.
I've got every Kalshi trade on the World Cup winner markets sitting in a database. Spent this week digging through the WC markets, about 200k trades across 10 teams, and a few things stood out that you just don't see if you only look at the closing price each day.
The USA one is the clearest. They opened at 9.2%, basically dead last. Over the next couple of weeks they nearly tripled that, but it didn't drift there. It happened on three specific nights after they played, and each time you can watch it move hour by hour. The night of the 19th there were 3,374 trades in four hours.
The Argentina one is my favourite. About half an hour after their first game the market hit 88%. Looks incredible if you screenshot it. Except it was 74 trades, and two hours later it was back to 10%. The daily average for that day came out at 46%, which is a number that means nothing at all, it's just the spike and the crash mashed together. Brazil did the exact same thing the next night. Every thin market does it after a win. Buyers pile in before anyone's around to sell.
France is the opposite and it's the one I'd actually trust. No spike, no drama, just 63k trades slowly buying it up from 19% to 36% over twelve days. Spain started at almost the same price and went nowhere, popped to 40% then faded back to 27%.
Wrote it all up with the charts here: https://www.probalytics.io/blog/wc2026-fills-market-signals
Fair warning, this is my own data (Probalytics, the data infra platformI run), but the post is just the analysis. Happy to pull numbers on any other team if people want.