State-legal sales of marijuana jumped nearly 20 percent to $5.4 billion last year, according to a market analysis report released Monday, which projects average annual growth of 30 percent through 2020.

Though sales of marijuana for medical use – allowed in about half of states – still dominate the national cannabis market, making up about $4.4 billion of 2015 sales, the growth rate for recreational marijuana was steeper, rocketing 184 percent to an estimated $998 million last year.

The overall economic impact of the booming quasi-legal sector and its ancillary businesses, which unlike their black market forerunners pay state and federal taxes, was not quantified in the report, which will be released in full later this month.

“It shows the legal cannabis industry is to be taken seriously,” says Troy Dayton, CEO of the ArcView Group, a prominent cannabis investor network that commissioned the report.

“These are serious numbers,” he says. “Where else do you find a multibillion dollar industry growing at 30 percent for the foreseeable future? It’s still early for people to make a big play in a market that’s growing like we only see a few times every century.”

John Kagia, one of the report’s primary researchers as director of industry analytics at cannabis data firm New Frontier, says sales figures were easy to calculate using state government data, with the exception of recreational sales in Oregon and medical sales in California and Michigan, for which his team created models with factors including illicit use rates and market maturity.

“We are at the very, very tip of the iceberg of what the industry could represent in 10 or 20 years,” Kagia says. “On that scale, we would compare this industry to others that have been truly transformative for our society.”

A robust legal market for marijuana generally concerns opponents of marijuana reform who suggest pot businesses make money by endangering children and public health, but is embraced by reformers as a laudable redistribution of money from drug gangs to ID-checking businessmen and public coffers.

Much of the recreational sales growth last year is attributable to the gradual opening of retail shops in the first states to treat the drug like alcohol, and projections for future sales growth take into account anticipated legalization of medical and recreational marijuana elsewhere in the next few years.

The 2014 data for recreational sales represented a full year in Colorado, but less than a half-year of sales from Washington, where shops opened later. The 2015 figures include a full year of sales in both states and a few months of projected Oregon sales, where medical pot dispensaries began selling recreational products in October. Anticipated 2016 recreational sales will include Alaska, which will unfurl its own market later this year.

Five states – Arizona, California, Nevada, Maine and Massachusetts – are likely to have legalization ballot initiatives in November, and Vermont appears on the verge of becoming the first state to legislatively legalize a recreational market.

Other states appear likely at some point in the near future to legalize marijuana. In Hawaii, for example, the state Senate’s Democratic majority leader, Sen. Kalani English, has reintroduced legalization legislation that he expects will pass within the next five years.

“Every year it moves a little bit further,” English said in a recent interview, explaining his state is known for high-quality cannabis and that Hawaii risks a brain-drain of experienced cultivators heading to the mainland U.S.

“In essence, we’ve been exporting our technology for many years, and we’ve watched other states benefit with huge tax revenue,” he says.

Marijuana businesses currently cultivate and transport the drug within state lines, as possession of marijuana for any reason outside limited research remains a federal crime, a fact that leads some investors and many financial institutions to think twice about working with the industry. But absent a major surprise – such as an unfavorable court ruling – the industry outlook remains positive, with front-runners in the 2016 presidential race saying they would continue the Obama administration's policy allowing for state autonomy.

Some of the nation’s largest states currently are unfurling regulated cannabis markets. In New York, medical pot became available this month, through the current law is regarded as extremely conservative. In Illinois, dispensaries opened late last year, and the state’s Republican governor blocked a bid to expand eligible conditions last week, citing the young age of the program. Both states are likely to see sustained campaigns to expand the list of eligible conditions.