With the Supreme Court's decision this week to scrap a federal ban on sports betting, Massachusetts lawmakers are considering ways to legalize it -- and bring millions in potential tax revenues to the state.

If they do, they will be legitimizing an industry that is already operating in the shadows on a massive scale, both nationally and in Massachusetts.

According to an estimate by H2 Gambling Capital, a betting market intelligence firm, U.S. gamblers made $196.2 billion in illegal sports bets in 2016, including both gambling with licensed off-shore websites and black market bookmakers.

"As context, this number is over 47 times the current US legal sports betting market, or nearly 1.5 times the total handle for all gambling taking place on the Nevada Las Vegas Strip in 2016," H2's report says. "This analysis means that 97 percent of all U.S. sports betting in 2016 was 'illegal'."

Other researchers have reached somewhat lower conclusions; the American Gaming Association has estimated that illegal sports betting is a $150 billion market in the U.S, and the firm Eilers & Krejcik Gaming has estimated $50 billion to $60 billion black market.

But H2's analysis, released in November of last year, portrays an industry larger in scale than significant sectors of the legal economy.

Americans spent more on illegal sports betting than on household appliances, televisions and baked goods combined, according to H2's report and data from the federal Bureau of Economic Analysis. The illegal betting market was four times larger than spending on fresh vegetables. In terms of other vices, it exceeded what Americans spent on store-bought alcoholic beverages and spending on tobacco.

Compared to other forms of recreation, illegal betting also came out ahead. Americans illegally bet about 14 times more money on sports than they spent going to the movies, and nearly eight times what they spent attending spectator sports.

And Massachusetts was a significant contributor, according to H2.

State-by-state statistics are hard to come by for black market betting websites and in-person bookmakers, who do not make a habit of releasing information about their customer base. H2, whose research has been cited in reports by The New York Times, The Economist and the professional services firm KPMG, calculated its black market estimate by applying industry assumptions of illegal gambling prevalence and average spending to the projected size of a fully regulated sports betting market in the U.S.

But for gray market betting -- sports gambling done on off-shore websites licensed in their own countries -- Massachusetts punched above its weight class.

Massachusetts spent the 8th most money of any state on grey market sports bets, according to H2, totaling $680 million in 2016. California and New York topped the charts, spending $3.6 billion and $1.57 billion respectively.

The Massachusetts Gaming Commission is well aware of the scope of illegal sports betting, and listed attracting gamblers away from black markets as a policy goal of legalization in a February white paper.

"While regulated sports betting in Nevada enjoys resurgent interest, sophisticated online illegal sports betting is easily available. A simple Google search for 'online sportsbook' returns numerous providers that offer online betting options to U.S. customers regardless of the legal status of sports betting in one's state," the commission's white paper says. "Many of these operators also provide mobile apps that integrate seamlessly with the sportsbook to allow for bettors to place bets wherever they have access to their smartphone."

"These black market operators may appear legitimate at first glance, but they are unlicensed and unregulated," the paper continues. "As a result, a disgruntled customer has limited recourse in the event of any complaint and no guarantee of any consumer protections for their money once it is sent to the operator."

Such betting made up about 10 percent of total illegal sports gambling in the country, with 69 percent going to black market online betting and 17 percent to illegal land-based betting, according to H2's analysis.

H2's calculation that 97 percent of 2016 sports betting in the U.S. was illegal is higher than previous estimates, but other studies have also concluded that gambling's black market dwarfs its legal counterpart. A 2014 analysis by the International Centre for Sport Security and the University of Sarbonne Paris concluded that 80 percent of the sports betting market was illegal.

H2 and the potential gaming operators watching Massachusetts closely for a chance to jump into the market view the industry on a macro scale.

But, as anyone who has worked an office job during March Madness knows, bans on sports betting have long been ignored when it comes to small scale and social gambling.

A 2016 Gallup poll found that 15 percent of American adults had participated in an office pool in the last year. It is a pastime that crosses age and cultural barriers -- and extends into the halls of the State House.

MassLive asked each member of the Joint Committee on Economic Development and Emerging Technologies, who would be the first lawmakers to review legislation legalizing sports betting, if they had ever bet money on sports in Massachusetts.

Most did not reply. Sen. Mike Barrett, Rep. Brian Murray and Rep. Keiko Orrall said they had not done so. Both Sens. Eric Lesser and Adam Hinds said they had participated in March Madness pools, with that being the extent of their sports betting. And Rep. Carole Fiola also said she had some small-stakes experience.

"The only sports 'bet' I've ever made was buying a 'square' at a house Super Bowl party," Fiola wrote in an email. "I recall I never won!"

Gov. Charlie Baker has also said he has never bet money on sports.