If the best government data is right, in 2018, 3.1 million people popped their weed cherry.  

Three million new weed users. That's a lot. 

Three million is an Iowa or Nevada's worth of people, or a Lithuania or Mongolia. It's 30 or 40 football stadiums, which, if they all exhaled together, would be pretty cool. 

For comparison, about 5 million Americans tried alcohol for the first time, including 2.4 million teens.

graph - past year initiates of drugs

[Number of people that tried a drug for the first time last year. Chart from the government's Substance Abuse and Mental Health Services Administration.]

Marijuana is illegal at the fedearl level, but legal in some form in most states. And it's long been the most-used drug besides alcohol. Forty-three million Americans used marijuana last year. 

Three million noobs who lit a joint, hit a bong, did a dab, or ate an edible for the first time is one reason U.S. legal weed sales are booming, to around $10 billion last year, up from around $6 billion in 2016.  

The numbers of new users every year has been steadily going up this century. About three million people tried weed for the first time in 2017, too, but only about 2.5 million each year in the three years before that. (Only.)

New pot users among 12 to 25 year olds held releatively steady.  

graph - marijuana initiates

[The number of Americans trying weed for the first time jumped between 2016 and 2017, from about 2.5 million noobs a year to more than 3 million (red line). The gains came from older Americans. Graph from SAMHSA.]

To get the data, the Substance Abuse and Mental Health Services Administration interviewed about 70,000 people face-to-face for its annual National Survey on Drug Use and Health in 2018. 

These findings may not be 100 percent accurate, critics say. People have to be truthful about illegal drug use when talking face to face with a government agent. And the data doesn't count homeless people and other who are hard to find. 

Still, these are about the best data that exist, and they're used by politicians, business folks and journalists. 

The most-reported finding from this study this year is that teen marijuana use is not rising. Teen pot use was actually higher in 2016 and peaked in 2002. "Marijuana use disorder" in teens also declined in 2018 — for the seventh straight year. So worries that legalization would spread weed use and abuse to kids haven't panned out. And use among young adults — 18 to 25 — is holding steady. 

It's older adults who are using, and, increasingly, trying weed for the first time.