Kalshi and Polymarket volume falls 14.5% after World Cup surge

Kalshi recorded $37.17 billion, down 7.3% from July's reported $40.1 billion. Polymarket and its U.S. platform produced a combined $8.16 billion, down 36.7% from $12.89 billion. The unequal declines left Kalshi responsible for more than four-fifths of the combined August total.

The comparison needs seasonal context. July overlapped with the FIFA World Cup, which ran from June 11 to July 19 and drew unusually high interest in sports-linked contracts. August volume was still well above May's $25.66 billion, making the result a pullback from a surge rather than a return to early-year activity.

Volume is not the same as adoption

Trading volume counts contracts changing hands and can include the same capital being recycled through repeated positions. It does not equal customer deposits, platform revenue or open risk. Comparisons across venues can also be affected by different contract designs, fee structures, reporting methods and rules for offsetting trades.

Regulatory pressure remains another variable. More than a dozen U.S. states have challenged or sought restrictions on sports event contracts offered by the platforms. At the same time, Kalshi continues to pursue distribution partnerships, including an arrangement with the U.S. Tennis Association around the U.S. Open.

The next test is whether event demand survives quieter months. Weekly active traders, open interest, fee revenue and non-sports activity would provide a fuller picture than headline turnover alone. The August decline is evidence that uninterrupted monthly growth ended; it is not, by itself, proof that the category has peaked.

A fair year-over-year comparison will also need consistent venue coverage. Polymarket's U.S. platform and shifting product availability can change the measured universe, so future dashboard revisions may alter historical totals even when the underlying trades do not change.