According to annual arrest data released Monday by the FBI, more than 1.53 million people were arrested on drug charges last year, nearly nine out of ten of them for simple possession, and nearly half of them on marijuana charges.

The data comes from the agency's Uniform Crime Reporting Program and it shows a decline in drug arrests from 2010. That year, 1.64 million people were arrested on drug charges, meaning the number of overall drug arrests declined by about 110,000 last year. The number of marijuana arrests is also down, from about 850,000 in 2010 to about 750,000 last year.

That still comes out to a drug arrest every 21 seconds and a marijuana arrest every 42 seconds, according to Law Enforcement Against Prohibition (LEAP), which took the release of the report as an opportunity to criticize 40 years of failed war on drugs policies.

"Even excluding the costs involved for later trying and then imprisoning these people, taxpayers are spending between one and a half to three billion dollars a year just on the police and court time involved in making these arrests," said Neill Franklin, a retired Baltimore narcotics cop who now heads LEAP. "That’s a lot of money to spend for a practice that four decades of unsuccessful policies have proved does nothing to reduce the consumption of drugs. Three states have measures on the ballot that would take the first step in ending this failed war by legalizing, regulating and taxing marijuana. I hope they take this opportunity to guide the nation to a more sensible approach to drug use."

No other single crime category generated as many arrests as drug law violations. The closest challengers were larceny (1.24 million arrests), non-aggravated assaults (1.21 million), and DWIs (1.21 million). All violent crime arrests combined totaled 535,000, or slightly more than one-third the number of drug arrests.