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America’s $6.7 billion marijuana habit, mapped

Glass containers display varieties of marijuana for sale on shelves at The Station, a retail and medical cannabis dispensary, in Boulder, Colo., Thursday, Aug. 11, 2016. (AP Photo/Brennan Linsley)

The marijuana industry is at a crossroads. Voters have approved recreational marijuana measures in eight states plus the District of Columbia. When these laws become fully implemented in the next few years, more than one in five American adults will live in places where they can walk into a store and legally purchase marijuana.

According to one estimate by ArcView Group, a marijuana industry consulting firm, the legal marijuana market rang up $6.7 billion in sales in 2016.

Legal or not, millions of Americans already use marijuana regularly. According to the most recent National Survey on Drug Use and Health, 8.3 percent of Americans age 12 and over -- 22 million people -- used marijuana on a monthly basis in 2015. And close to 37 million people used marijuana at least once that year.

The latest data release from that survey breaks those numbers down even further, looking at marijuana consumption at the state level. It finds that there's considerable variation in the prevalence of marijuana use by state.

In the 2014-2015 period (years are paired for state-level data to provide bigger sample sizes), nearly a quarter of people in places where recreational pot is legal -- like D.C. and Colorado -- used some form of marijuana at least once a year.

That's nearly double the national average, and it's close to three times the rate for the most pot-abstinent states, like Alabama, Mississippi and Iowa, where around 8 or 9 percent of people age 12 and older use pot yearly.

Generally speaking, the Northeast and the West Coast are the two major marijuana hotbeds in the country. Marijuana use between the coasts is generally lower, with the notable exception of Colorado.

The state-level data shows that places with the most marijuana use generally have some form of legal medical or recreational marijuana available. This is likely a two-way street: places with lax attitudes about marijuana use are more likely to approve legal marijuana, and marijuana availability probably leads to more lax attitudes about use.

It's also instructive to compare the map of marijuana use against the national drinking map. One notable difference is that people in the northern plains states are heavy drinkers, but more abstemious when it comes to pot.

There are similarities too. Alabama and Mississippi are in the bottom tier of states on both alcohol and pot. New England, on the other hand, ranks high on both measures.

Public health experts generally wag their fingers at folks who drink a lot, smoke a lot, or even worse -- do both. Yet New England consistently ranks among the most healthy regions of the United States, taking into account a variety of measures like poverty, immunization, education, medical care and yes, drug use.

Conversely, drug- and alcohol-averse Southern states usually show up at the bottom of those rankings (thank God for Mississippi, as the old social science adage goes).

None of this is to suggest that high rates and drug and alcohol use are driving good public health outcomes in the Northeast. But the data above are a helpful reminder that it's generally a bad idea to look at any public health metric in isolation.

What we can learn about legal marijuana from Washington, Colorado and Oregon. (Video: Daron Taylor, Danielle Kunitz/The Washington Post)