States completely differ in their approaches to marijuana: some arrest thousands of people each year, while others barely arrest anyone at all.

Some of the most solidly blue states — New York, Illinois, and Maryland — make the most arrests each year, along with deep-red Louisiana and Mississippi, according to a compilation of federal data from Addiction-Treatment.com.

Even when controlling for how many marijuana users reportedly live within a state, arrests remained high in New York, Illinois, Maryland, Louisiana, and Mississippi.

Now, these arrests don't always lead to jail and prison time. Estimates put only 40,000 people for marijuana in state and federal prisons, and many of those were involved with trafficking, not just possession.

Laxer state policies play a role sometimes, but not always

A lower number of arrests can in some cases reflect a state's more relaxed policy approach to marijuana. Alaska, for instance, decriminalized marijuana in the 1970s, and in Washington the drug was legal for medical purposes in 2012. (The drug was not fully legal in any state until the end of 2012, when some arrest data for the year had already been collected.)

But the arrest statistics in other cases defy expectations set by state policy.

New York, for example, decriminalized marijuana in the 1970s, but police in the state arrested thousands for possessing the drug in 2012. As the Marijuana Policy Project explained, there is an exception in New York's decriminalization law for marijuana that's within public view. Police officers reportedly used that exception to arrest people, particularly minorities, by getting them to empty their pockets during searches and expose marijuana that would otherwise remain hidden.

In other words, state policy is important, but how law enforcement treats the law can be just as important.

Relaxed state policies can reflect a higher population of marijuana users

The states with the most relaxed marijuana policies are often the states with the most marijuana users. From a certain perspective, that makes sense: marijuana users might flock to states with more relaxed laws, and a state population with more marijuana users might be more predisposed to allow the drug.

These numbers for regular pot users also explain marijuana legalization advocates' next targets for ballot and legislative efforts. As a red state, Alaska might seem like an odd choice for a 2014 ballot initiative that would legalize marijuana. But when looking at the high amount of reported pot users in the state, Alaska appears to be a more sensible target.

From that perspective, the only real surprise is that legalization advocates aren't putting more public efforts into Montana. There, marijuana possession still carries jail and prison time despite the state's high population of pot users. Then again, based on the arrest statistics, Montana's marijuana laws aren't being enforced that much in the first place.