Investors follow their noses. They know the smell of money. These days, it smells something like freshly cut grass.

The U.S. legal marijuana market is blazing.

So found ArcView Market Research, a firm focused on America’s fast-growing legalized cannabis industries.

According to ArcView’s new report, created in collaboration with New Frontier Data, U.S. sales grew 17 percent in in 2015 — from $4.6 billion in 2014 to $5.4 billion last year. That’s more than Americans spent over the same period on marijuana-companions like Cheetos, Doritos, and Funyuns, the Washington Post calculated.

The firm projects $6.7 billion in sales this year — a 25 percent jump — and $21.8 billion by 2020. That, of course, is dwarfed by the size of the illegal marijuana market, which by some estimates was worth up to $30 billion in 2012.

ArcView, which is based in Oakland, California, where recreational marijuana remains illegal, produces the most widely cited reports on legal marijuana markets, which are expanding sharply because of shifts in popular opinion and the growing number of states that have decriminalized usage. “Investors, regulators, and business operators are our biggest audience,” ArcView CEO Troy Dayton told Foreign Policy.

The majority of Americans now support marijuana legalization, according to Gallup and other polls. Alaska, Colorado, Oregon, Washington state, and Washington D.C. have legalized the drug for adult use, while nearly half of states allow the use of medical marijuana. Cannabidiol, a marijuana product known as CBD, has also been legalized widely. Some NFL coaches, like Super Bowl champion Pete Carroll of the Seattle Seahawks, have called on sports leagues to explore the use of marijuana as an alternative painkiller. Around 86 percent of Americans live in a state where some degree of marijuana use is legal. More states are likely to legalize adult recreational use in the near future, including Arizona, California, Connecticut, Maine, Nevada, New Hampshire, and Rhode Island.

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Colorado expects to have generated $135 million in state revenue off of marijuana in 2015 alone.

Ohio voted down a legalization bill in 2015, showing that the trend has its limits. But the law failed in large part due to inbuilt stipulations that would have legally enshrined a 10-company marijuana oligopoly, which many voters opposed.

Medical markets have also contributed to growth, as new research produces promising findings for expanded clinical applications.

While some twists, such as the election of a new presidential administration unfriendly to the legal cannabis industry’s rise, or increases in regulation, could dampen growth, most foreseen developments, from the integration of new technology to the growth of international markets, are likely to have mixed to positive effects on the U.S. market, according to the report.

The illegal marijuana trade has long been an international enterprise. The legal trade could take a turn in that direction as the debate advances around the world. Israel has approved a range of medical applications. Canada, under newly elected Prime Minister Justin Trudeau, has announced legalized possession, with full legalization in the works. Private consumption is legal in many parts of Spain. Australia is expanding its scientific and medical programs. Uruguay fully legalized the drug in 2014, and its market is slowly activating. Jamaica has legalized cultivation for personal use. A new law in Colombia builds on existing personal cultivation and use statutes by allowing legal export and import of the drug for scientific and medical purposes.

“The U.S. was the main exporter of marijuana prohibition, in terms of treaties, rhetoric, and relations,” Dayton said. “As more states in the U.S. pass legalization, the federal government won’t really have a leg to stand on. If you’re somebody looking to invest in really early markets, increasingly, those pioneering investments will be outside the U.S.”

Although the continued, rapid growth of legal marijuana markets depends largely on decisions by lawmakers at all levels of government, the cash bonanza currently underway seems to be in an early stage, set to go supernova as the lucrative drug moves slowly off the black markets and into the regular, regulated ones. But marijuana’s future remains rife with uncertainty and contradictions. It remains a Schedule I illegal substance under federal law.

Photo credit: Robyn Beck/AFP/Getty Images