Sports betting will likely occur through exchanges and retail brokerages like Robinhood Markets Inc. in the future, the head of North American markets at Nasdaq Inc. said on Thursday. Nasdaq in June took a stake in Sporttrade, a start-up that plans to launch a sports betting app in New Jersey by year-end, and last month the exchange operator said it was providing the company with market surveillance technology. Bringing an exchange model to sports betting will add competition and transparency to the industry, now legal in 25 states, with large states like California, Florida, and New York looking at it, and by some estimates could be worth $37 billion by 2025, Nasdaq’s Tal Cohen said at a Securities Traders Association conference. “In terms of competition, we’ll have liquidity providers, market makers, compete for business, which means better prices and better odds, and lowers friction, and also means there’s more data …