A few days before Sunday's World Cup Final, combined Kalshi and Polymarket open interest (OI) is down 20% from its peak of ~$2 billion at the beginning of July.
On a smoothed weekly basis, total OI ran from $1.2 billion in late May to nearly $1.8 billion in the week ending July 5, then fell to around $1.5 billion by the week ending July 19.
Kalshi’s sports volume peaked at ~$9 billion in the week ending July 5 and fell to around $4 billion by the week ending July 19, down about 55%. While Polymarket’s sports volume peaked near $2.3 billion and dropped to $740 million over the same span, down nearly 70%.
Sports accounted for roughly 80% of both platforms’ total volumes throughout the tournament, as all eyes were on the World Cup. On Sunday, Spain defeated Argentina 1-0 to win the country's second-ever World Cup title.
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