They don’t call it the Green Rush for nothing.

New research suggests legal cannabis sales in North America are growing more quickly than experts anticipated.

Arcview Market Research reports that retail cannabis sales will leap 33 percent over 2016’s totals to hit $10 billion this year; a kind of rapid growth researchers hadn’t predicted.

They say next year’s numbers could escalate even higher.

“Aside from cryptocurrency, there is simply no other industry changing as rapidly or as unevenly as the cannabis sector,” said Troy Dayton, CEO of The Arcview Group.

Recreational cannabis legalization will go into effect in Canada in July, while Nevada is expected to ramp up its efforts for cannabis tourism.

California is expected to be the real game-changer, however, with recreational cannabis set to become legal in January.

BDS Analytics’ GreenEdge point-of-sale tracking service reports that California’s medical marijuana market is already as big as the total markets in Colorado, Washington, and Oregon combined.

With California's contributions on the horizon - along with a growing confidence that several other states may legalize sooner than later - Arcview now predicts the legal cannabis market will hit sales of $24.5 billion by 2021.

h/t Fortune