Here’s a nice chart from Andrew Sullivan on marijuana consumption in Colorado. It illustrates a point that has been made many times by drug policy analysts such as Mark Kleiman and Beau Kilmer: The total volume of pot consumption is accounted for almost entirely by users who smoke every day or nearly every day. Envisioning how different stakeholders would respond to this evidence can be helpful both for appreciating the impossibility of value-free evidence-based policy and for understanding one of the basic dilemmas of legal marijuana regulation.

AT THE PUBLIC HEALTH CONFERENCE: “Colleagues, you can see from this chart that not all marijuana users are of equal concern to us. Some people use the drug rarely, and we know that such users tend to be high social capital individuals who could set their lives right in the unlikely event that they did develop a drug problem. So we should focus instead on these heavy users in the bottom two bars of the chart, who tend not incidentally to be people with less education, less income and poorer access to health care. The evidence we have shows that the primary risks of this drug, for example marijuana dependence, mental health problems and poor school and work performance, are concentrated in the subset of people who use every day or almost every day. Let us therefore resolve to keep the size of this group as small as possible through high taxes that discourage heavy consumption, caps on THC content that reduce the ability of the drug to promote dependence and limits on advertising and points of sale in vulnerable communities.”

AT THE CORPORATE BOARD MEETING: “Well friends, you can see from this chart that not all of our customers are of equal concern to us. We can’t make much money from the people in the top few bars of the chart, so we should focus mainly on the heavy users who provide us the bulk of our revenue. We need to move as much of the population as possible into this high-revenue bracket. So let’s all agree to press for lower taxes, higher THC content and as much advertising and as many retail locations as possible in the communities where our best customers tend to live.”

AT THE STATE LEGISLATURE: “Fellow committee members, as you know we have seen this chart twice today, once when the public health advocates visited and again when the marijuana industry lobbyists visited. Both groups agreed on the evidence but they wanted us to respond to it in opposite ways. And that’s not the end of what we have to consider. The state budget analyst’s office has calculated that almost 90% of the marijuana tax revenue we wanted from legalization comes from the people in the bottom bars of this chart. We care about public health but if we implement policies that make too many of those heavy marijuana users quit, the tax revenue hit we will take might force us to sacrifice other important priorities.”