The impact of mobile sports betting is being considered by many states.Betting on smartphones could increase total U.S. sports gambling revenue by an estimated $9 billion, but some worry about impact on casinos.

Now that states are free to craft laws legalizing sports betting, the latest question is whether to enter the potential $9 billion mobile-betting market. Americans legally gambling on this weekend’s World Cup final and other athletic competitions primarily are doing so in person at a limited number of casinos. Increasingly, though, gamblers in other countries are placing wagers from their smartphones.

In the U.K., the world’s largest legal sports-betting market, revenue from online wagers has more than doubled over the past five years and now represents 60% of the market, whereas revenue from in-person betting has fallen by about 12% over the same period, according to data from Gambling Compliance, an industry research firm.

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