libertarian fantasy into a mainstream cause. Many state laws have changed as well. Over the last quarter-century, 10 states have legalized recreational marijuana, while 22 states have legalized medical marijuana.

So why has public opinion changed dramatically in favor of legalization? In a study published this February, we examined a range of possible reasons, finding that the media likely had the greatest influence.

It’s Not About Use, Geography, or Demographics

Our study ruled out a few obvious possibilities.

For one, it’s not about marijuana use. Yes, cannabis use has increased. Data from the National Survey on Drug Use and Health show that, in 2002, about 10 percent of adults reported using cannabis the previous year. By 2015, 13.5 percent reported using. But that increase is too small to have had much of an impact on attitudes.

And it’s not about older, more conservative Americans being replaced by younger generations who are more familiar with marijuana. Both younger and older people developed more liberal views about the legalization of marijuana at a similar pace over the last 30 years. In this way, changes in attitudes about marijuana legalization mirror recent increases in support for LGBTQ individuals.

We looked to see if people who lived in states where it was illegal, but resided next to ones where it became legal, were more likely to have changed their views. But the rate of change has been no different in states that legalized marijuana than in others.

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