Marijuana is the top cash crop in the US, a report released on Monday says.
It says that despite intensive eradication plans, $35bn (£18bn) worth of the illegal drug is produced a year - more than corn and wheat combined.
The study was prepared by Jon Gettman, a public policy analyst who advocates reform of US marijuana laws.
Activists seeking the decriminalisation of the substance, say the report backs the need for change, a position rejected by government officials.
'Inherently harmful'
Using government reports, Mr Gettman estimates that 10,000 metric tons of marijuana are produced annually in the country.
"Marijuana has become a pervasive and ineradicable part of the economy of the United States," Mr Gettman - who has in the past campaigned for marijuana to be removed from a list of drugs considered to have no medical value - says in his report.
"The focus of public policy should be how to effectively control this market through regulation and taxation in order to achieve immediate and realistic goals, such as reducing teenage access."
The report was welcomed by the Marijuana Policy Project (MPP), which said it showed that "marijuana laws are a complete failure".
"Our nation's laws guarantee that 100% of the proceeds from marijuana sales go to unregulated criminals rather that to legitimate businesses that pay taxes to support schools, police and roads," said MPP executive director Rob Kampia.
But Tom Riley, a spokesman for the Office of National Drug Control Policy, rejected any economic arguments for legalising marijuana saying marijuana use was an "inherently harmful activity".
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