Kalshi surpassed $1 billion in monthly contract volume in mid-September, coinciding with the start of the NFL season. It then saw$538 million worth of contracts traded Sept. 27-28. According to LegalSportsReport , 98% of that volume came from sports-related contracts.Prediction markets have been around for a few years, but they gained momentum following the last U.S. presidential election. Their popularity has even gripped Wall Street, where investors and strategists increasingly rely on their odds as a ki ...