Prediction-market activity tied to the World Cup lost momentum in the days before the final, according to data cited by The Block, with combined open interest across Kalshi and Polymarket down 20% from an early-July peak of about $2 billion.
On a weekly smoothed basis, total open interest rose from roughly $1.2 billion at the end of May to nearly $1.8 billion in the week of July 5. It then pulled back to about $1.5 billion in the week of July 19.
Trading volume dropped more sharply than open interest
The decline in volume was steeper. Kalshi’s sports trading volume fell from about $9 billion at its peak in the week of July 5 to around $4 billion, a drop of about 55%.
Polymarket posted a larger percentage decline, with sports volume falling from roughly $2.3 billion to $740 million, or close to 70%.
During the tournament, sports contracts accounted for about 80% of total trading volume across the two platforms. On July 19, Spain beat Argentina 1-0 to win the World Cup title.
DeFiOasis data shows mixed outcomes for traders
DeFiOasis said about 194,000 addresses traded in Polymarket’s World Cup winner market. About two-thirds of those addresses ended up with losses.
Among the profitable traders, 54 addresses made more than $100,000, including five that made more than $1 million. On the losing side, 43 addresses lost more than $100,000.
The report said prediction-market activity is expected to remain subdued until the next major catalyst arrives: the U.S. midterm elections in the fall.