In his latest anti-cannabis-legalization screed, (behind the Wall Street Journal paywall), written with a former federal prosecutor named Robert White, William Bennett writes:

Mark A.R. Kleiman, a professor of public policy at the  the university of California, Los Angeles, has estimated that legalization can be expected to increase marijuana consumption by four to six times. Today’s 2.7 million marijuana dependents (addicts) would thus expand to as many as 16.2 million with nationwide legalization.

Now, if Bennett wants to make silly predictions, and if Rupert Murdoch wants to publish them, all I can say is, “It’s a free country.” But I think I’m entitled to protest when he attributes that silliness to me. It’s hard to count how many ways that short paragraph is wrong, but the central points are simple:

1. An estimate of the possible change in quantity consumed is not an estimate of the change in the number of dependent users. Consumption can also grow because the amount consumed per dependent user increases.

2. Even most dependent users are not, by any reasonable definition, “addicts.”

3. The large estimated impact on consumption depends the  factor-of-ten price decrease (to about $1-2/gm. for moderately potent product) that would result if cannabis were treated like an ordinary commodity. If taxation or production limits prevent such a drastic decrease, the effect of legalization on consumption would be much smaller.

According to a phone conversation I had this morning with Robert White, the source of the “estimate” is p. 25 of Drugs and DrugPolicy. Here’s the actual relevant text from that page:

We might expect something like four to  six times as much cannabis to be consumed after legalization as is consumed now.

That’s the culmination of a somewhat complex argument (starting on p. 22) arguing against the claim that drug laws have no impact on consumption. If cannabis were produced and sold on the same legal basis as tea, the price could be about one-tenth of the current illicit-market price.  For reasonable values of the price-elasticity of demand, such a factor-of-ten decrease in price might lead to something like a threefold increase in quantity consumed. Obviously that’s speculation, because we have no experience with prices that low, or with the consequences of the shift between smoked herbal product and vaporized concentrates of the consumption of  cannabis in edible and potable forms.

Other factors would change with legalization in addition to price, all in the direction of encouraging more use: increased access, better product quality, product innovation, marketing effort, decreased social stigma, and decreased legal risk. De facto legalization without a price decrease in the Netherlands has been associated with approximately a doubling of prevalence, though to levels still very low by U.S. standards.

Combining those non-price factors – which shift the demand curve – with the movement along the demand curve as price falls might lead to something like a four-to-sixfold increase in total quantity consumed, compared with a strict prohibition. (Of course, places such as California don’t actually have strict prohibition today.) That seems to me like a reasonable estimate, no more likely to be too high than too low, though of course the error band is enormous. But that doesn’t necessarily mean a proportionate increase in either the number of total users or the number of problem users; in fact, what we’ve been seeing over the past decade has been an increase in cannabis use at the intensive margin, among already-heavy users. The number of people meeting diagnostic criteria hasn’t moved much, but days of use and quantity per use-day have both increased.

The calculation of an increase in the number of “addicts” is entirely Bennett and White’s  based on confusing a change in the quantity consumed with a change in the number of users, and assuming (without any basis) that a constant fraction of consumers become “addicts.” But they write it in a way that suggests, without actually saying, that it is my calculation. (And of they attribute to me alone, though the book has three authors.)

In fact, an estimated 2.7 million Americans today meet diagnostic criteria for cannabis dependence. (Perhaps unexpectedly, only about half of daily cannabis users meet diagnostic criteria.)   And dependence” is typically transient rather than chronic. Chronic, relapsing cannabis use disorder – which is what “addiction” means, if it means anything except “Bill Bennett wants you to be very afraid” – probably claims fewer than 1 million American victims today. And that’s after 15 years of rapid growth in heavy use under a weakening system of prohibition.

So to assert the existence of 2.7 million cannabis “addicts” and then sextuple to estimate 16.2 million “addicts” post-legalization is flat-out silly. Even putting aside its false precision, the number can’t be right, unless you expect chronic, relapsing cannabis dependence to become much more common than chronic, relapsing alcohol dependence. The annual prevalence of total alcohol dependence (again, most of it not chronic) is estimated at something under 10 million. (3.8% of the 80% of the U.S. population of 318 million that is over 15). Does any sane person expect cannabis dependence to become more common than alcohol dependence? Seriously?

When I talked to Robert White this morning, he was aware that I had called out Bennett and a different co-author for a previous attempt to misrepresent my views, but remained utterly unconcerned and unapologetic, resting on the fact that the article never explicitly attributes the “16.2 million” number to me, though of course it’s deliberately written (the key-word is “thus”) to claim me as expert authority for that prediction.

It’s the old hit-and-run: put up nonsense, and trust the capacity of your lie to get halfway around the world before the truth has had time to put its shoes on.

These folks could teach Principles of Sliminess at Slug University. I guess Bennett must not have read the chapter on honesty in The Book of Virtues.

Footnote Yes, I have a call in to the WSJ op-ed desk, demanding a retraction. And of course they’re going to tell me they don’t take any responsibility for what they publish in the opinion section. And yes, I’ll try writing a letter, and of course they will tell me they don’t have enough space to let me explain how many ways Bennett and White got it wrong. And that post will be on line forever, so that 10 years from now I’ll have to explain, “No, I never predicted that legalization would lead to 16 million cannabis addicts.”

[Cross-posted at The Reality-Based Community]

Mark Kleiman

Mark Kleiman is a professor of public policy at the New York University Marron Institute.