Polling tells us that a majority of Americans now favor legalizing marijuana and regulating it like alcohol. But how much support is really out there?
Here are a few tips for reading pot polls.
First, a single poll does not a megatrend make.
Back in 2013, a Gallup poll found that 58 percent of American adults favored legalizing marijuana, a spectacular 10 percentage point jump from the 48 percent who told Gallup they favored legalization in 2012, and the largest pro-pot majority ever recorded in a national poll. Legalization advocates rejoiced. But when Gallup asked the same question a year later in 2014, only 51 percent said they favored legalization. But then in October 2015 the number was back up to 58 percent. And again no other poll has found support that high.
So what’s going on here?
A likely explanation is that the 2013 Gallup number was an “outlier.” When the press reports that a poll has a margin of error of, say, plus or minus 4 percent, it’s over-simplifying. What it should be saying, and what professional pollsters will say, is that their poll had “a margin of sampling error of plus or minus five percentage points at the 95 percent confidence level.”
The “95 percent confidence level” is what’s important here. What it means is that there’s a 95 percent chance that the poll’s results are accurate within a margin of plus or minus four percentage points. Put another way, there is one chance in 20 that the poll’s results are off by more than plus or minus four percentage points. Such polls are called “outliers.”
A clue that the 2013 Gallup poll was an outlier was the size of the jump from 2012. Most marijuana polls have shown slow but steady progress toward legalization. Also, legalization polls by other pollsters taken in 2013 and 2014 showed support for legalization usually in the 50 percent to 52 percent range or lower.
So is this year’s Gallup result also an outlier? Possibly, but less likely than in 2013. For one thing, a poll by Morning Consult, also taken in October 2015, found 55 percent support for legalization, closer to the Gallup results. Moreover, Morning Consult surveyed registered voters only, as opposed to Gallup’s all adults survey. A registered voters poll usually comes out a bit more conservative than an all adults poll, which may account for some of the three-point difference.
Polls for CBS News and Pew Research in 2015 both put support for marijuana legalization at 53 percent among all adults. A Fox News poll of registered voters put the figure at 51 percent.
All three of those polls showed support for legalization ticking up a point or two since they asked the same question in 2013. When several different polls are all moving in the same direction over the same time frame, the trend is probably real, even if the individual results vary a bit.
And what accounts for the movement? Demographics more than anything. In virtually every poll on marijuana legalization taken in the last five years the two sub-groups most opposed to legalization are Republicans and Americans over 65.
People’s beliefs on social issues like abortion and pot legalization tend to form early in life and get locked in. If they change at all, they tend to change slowly and incrementally.
Which means the greatest driver of attitudinal change on social issues is demographic change. Every year about two million Americans die of old age and four million Americans come of (voting) age.
In the latest Gallup Poll 71 percent of Americans aged 18-34 favored legalization, while only 35 percent of Americans aged 65 or older did.
Legalization advocates shouldn’t get too cocky though. The 65-plus geezers are the group most likely vote. The 18-34-year-olds are the group least likely to.
