Today, for the first time ever, Gallup reports that a solid majority of Americans are in favor of legalizing marijuana. I've drawn my own chart of Gallup's data because I think their chart doesn't really give a good sense of just how quickly public opinion on this is changing.
I have a rule of thumb that favorability ratings need to reach about 65 percent before you hit a tipping point where a major social change starts getting codified into law nationwide. There's nothing magic about this threshold. It's just a general sense based on previous issues similar to this. And as you can see, public opinion isn't merely rising on marijuana legalization, it's accelerating. The rate of increase has gone from about 0.5 points per year in the 90s to 1.5 points in the aughts to 4 points so far in the teens. If this keeps up, we'll pass the 65 percent threshold by 2016 or so.
There's a lot of noise in polls like this, and we might see a bit of regression to the mean in the next few years. And Mark Kleiman offers a few other cautionary notes here. So 2016 is hardly a sure thing. But 2020? That seems like a pretty safe bet in most of the country. By coincidence, this was my horseback guess when I wrote about marijuana back in 2009, and it looks like I don't have any good reason to change my mind on that.