LOS ANGELES - Marijuana is the most valuable cash crop in the United States, worth more to its growers than corn and wheat combined, according to a new report by a leading American drug reform lobbyist that cites the US government's own figures.
Decades of government efforts to crack down on both the cultivation and consumption of pot have had a counter-productive effect, since even the most conservative government estimates suggest domestic marijuana production has increased tenfold in the past 25 years.
It is the leading cash crop in 12 states, and one of the top five crops in 39 states.
The report's author, Jon Gettman, says it is "larger than cotton in Alabama, larger than grapes, vegetables and hay in California, larger than peanuts in Georgia, and larger than tobacco in South and North Carolina".
California accounts for almost a third of all US production.
It is a major economic force in the state, especially in the redwood forests in the north, where the smell of weed wafts unmistakably down the streets of several towns.
Marijuana remains popular with the baby boomer generation, which first experimented with it in the 1950s and 1960s.
And its use is booming among teenagers and young adults, especially as alcohol cannot be sold to under 21s.
US Marijuana cultivation is worth more than US$35bn (NZ$50bn) per year.
And that is a conservative estimate, based on government price surveys, Mr Gettman says.
Corn, the largest legitimate crop, is worth just over US$23bn and soybeans around US$17bn.
"Despite years of effort by law enforcement, they're not getting rid of it," Mr Gettman told the Los Angeles Times ahead of his report's publication yesterday in The Bulletin of Cannabis Reform.
"Not only is the problem worse in terms of magnitude of cultivation, but production has spread all around the country. To say the genie is out of the bottle is a profound understatement."
Figures issued by the State Department and other government agencies show marijuana production increased from an estimated 2.2 million pounds in 1981 to at least 22 million pounds.
Some estimates put the current crop as high as 50 million pounds.
Since the presidency of George Bush Snr in the late 1980s, official policy has been one of zero tolerance of all illegal narcotics.
Recently, the federal government has been unforgiving of the medical marijuana movement, and federal agents have raided numerous marijuana farms that were fully licensed under state law.
It has not cut down use of the drug.
Mr Gettman and other activists argue that it might be time to legalise the entire industry and subject it to proper regulatory control and taxation.
"The fact that marijuana is America's number-one cash crop after more than three decades of governmental eradication efforts is the clearest illustration that our present marijuana laws are a complete failure," said Rob Kampia, executive director of Washington's Marijuana Policy Project.