What happened: Football-related trading reached about $416 million in August, more than double the $205.2 million recorded a year earlier. New exchanges, combo contracts and broader advertising are expanding the market before the Sept. 9 regular-season opener.

Why it matters: September football volume rose more than tenfold last year, making the NFL calendar a major test of whether recent growth can persist. Legal pressure is also mounting after the 9th Circuit on Friday declined to let resume sports-event trading in Nevada without a state license.

What to watch: Trading activity after the Sept. 9 opener will show whether football volume can clear the projected $4 billion threshold. Court challenges could determine how widely the contracts remain available.