In trying to justify his proposed regulation banning large-size sodas, New York Mayor Michael Bloomberg cited the work of economists Brian Wansink and David Just. In this recent Atlantic article, Wansink and Just explain that he got their work wrong:

New York City’s mayor proposed a restaurant ban for any soft drink over 16-ounces. The hope is that by banning big drinks people will drink less and weigh less. He and others cited our research as the science behind the policy. Indeed, a dozen of our studies show when you randomly give people large sizes of food like popcorn and French fries, they overeat…. There’s a critical difference between the lab and Lexington Avenue that the mayor’s office didn’t account for: when Joe the Plumber and Bob the Banker buy soft drinks, they buy the size they want. They aren’t randomly forced to take a 44-ouncer when they really wanted a 12-ouncer. Moreover, their Coke or Pepsi doesn’t magically refill itself. If that happened, they’d overdrink. Instead, most restaurants give us a choice of a small or large drink — just as nearly every fast food outlet gives us a choice of small, medium, or large fries, and every movie theatre gives us a choice of small, medium, or large popcorn. People who want a little buy a little, and people who want a lot figure a way to get it. Yes, we have found that when people are given larger portions, they do drink or eat substantially more. But to claim that these results imply that the ban will be effective is to ignore our larger body of work. In our experiments, subjects were given larger or smaller portions of food in a dining or party setting, where they were unlikely to notice portion size. It is exactly because participants weren’t paying attention that we got the results we did. The mayor’s approach, however, overtly denies people portions they are used to be able to get whenever they want them. In similar lab settings, this kind of approach has inspired various forms of rebellion among study participants. For example, openly serving someone lowfat or reduced-calorie meals tends to lead to increased fat or calorie consumption over the whole day. People reason that because they were forced to be good for one meal, they can splurge on snacks and desserts at later meals.

As I explained in my previous post on this subject, paternalistic policies are not going be able to prevent obesity merely by restricting sodas or some other specific food or drink. People who like sugary or fatty foods will simply gorge on something else. The only potentially effective paternalistic solution is comprehensive regulation of people’s diets and possibly exercise as well.

I would oppose the soda regulation and others like it even if they did improve health. Individuals should be able to decide for themselves to what extent they are willing to accept health risks in order to satisfy other preferences. I get less than the optimal amount of exercise in part because I spend a lot of time reading and writing. As a result, I am less healthy than I might be otherwise. But that is a tradeoff I should be able to make in a free society. The same goes for people who are willing to accept health risks for other reasons – including because they want to continue eating the types of food they enjoy.

That said, I can at least understand the case for paternalistic regulations that have genuine health benefits. Paternalistic regulations that don’t even work are just gratuitous infringements on freedom without any justification at all.

UPDATE: In my previous post, I explained why these kinds of paternalistic regulations can’t be justified by the existence of externalities caused by government subsidization of health care.

UPDATE #2: For a more extensive look at the relevant evidence showing that soda restrictions are unlikely to improve health outcomes, see this article by well-known law and economics scholars Jonathan Klick and Eric Helland.

UPDATE #3: In the initial version of this post, I accidentally got David Just’s first name wrong. Thanks to readers for pointing this out. The mistake has now been corrected.