After the World Cup, Kalshi and Polymarket's open contracts fell back 20% from their peak

According to data from The Block, in the days leading up to the World Cup final, the total open interest (OI) of Kalshi and Polymarket combined has decreased by 20% from a peak of about $2 billion in early July. When smoothed weekly, the total OI rose from about $1.2 billion at the end of May to nearly $1.8 billion in the week of July 5, before falling back to about $1.5 billion in the week of July 19.

The decline in trading volume was even more severe: Kalshi's sports trading volume dropped from a peak of about $9 billion in the week of July 5 to about $4 billion (a decrease of about 55%), while Polymarket fell from about $2.3 billion to $740 million (a decrease of nearly 70%). During the event, sports-related trading accounted for about 80% of the total trading volume on both platforms. On July 19, Spain defeated Argentina 1-0 to win the World Cup.

According to statistics from DeFiOasis, approximately 194,000 addresses participated in Polymarket's World Cup champion market trading, of which about two-thirds incurred losses, with 54 addresses making over $100,000 (including 5 over $1 million), and 43 addresses losing over $100,000. It is expected that the activity in the prediction market will remain low until the next major catalytic event (the U.S. midterm elections in the fall).