THERE has long been enthusiasm among the "nudge" behaviouralists for the posting of calorie content in restaurants. The availability of this information, it is assumed, will encourage diners to choose healthier options, thereby improving public health, without heavy-handed government limits on what can actually be sold and consumed. And so there was a great deal of disappointment when early results out of New York City, where mandated calorie count information was introduced in 2008, failed to show the expected decline in calories consumed:

The results were pretty dismal: only about half the respondents even noticed the calorie counts and only 15% said they influenced their choice. But the receipts told an even more dismal story: overall, people actually purchased more calories after the law went into effect. The results aren't statistically significant, though, so basically all the researchers can really say is that the law (so far) hasn't had any effect. The only glimmer of good news is that among people under 35, respondents who noticed the labeling did seem to cut back a bit. No other subgroup showed any effect.

But perhaps that initial analysis underestimated the effect of the programme. Here's a new piece of research from NBER, by Bryan Bollinger, Phillip Leslie, and Alan Sorensen:

We study the impact of mandatory calorie posting on consumers' purchase decisions, using detailed data from Starbucks. We find that average calories per transaction falls by 6%. The effect is almost entirely related to changes in consumers' food choices—there is almost no change in purchases of beverage calories. There is no impact on Starbucks profit on average, and for the subset of stores located close to their competitor Dunkin Donuts, the effect of calorie posting is actually to increase Starbucks revenue. Survey evidence and analysis of commuters suggest the mechanism for the effect is a combination of learning and salience.

That is what we'd expect to see; after all, consumers seem to significantly underestimate the calorie content of junk food, occasionally by thousands of calories. What's interesting is that Starbucks actually benefitted financially, relative to nearby competitors, from posting this information. That suggests that firms should be quick to adopt calorie posting in places where it's not yet mandated. And, oddly enough, the government mandate seems to have turned up a few twenty dollar bills, just lying around on the sidewalk.