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Robert Frank on Soda Taxes

A couple days ago, the Cornell economist Robert Frank weighed in at the New York Times on Bloomberg's soda ban.  

The first part of the article is mainly about negative vs. positive freedoms.  Frank wants the government to guarantee ​positive freedoms (how many, I'm not sure) whereas I'd prefer the government primarily focused on guaranteeing negative liberties.  This is an old debate (I'm reminded of the chapter in Hayek's Road to Serfdom where he talked about the successful efforts to redefine the word "freedom.") and although I disagree with Frank, I at least understand where he is coming from (aside from the ad hominem connections between soda and tobacco).

What confuses me (because he's an economist) are Frank's economic arguments for a soda tax.  ​

In the 2nd to last paragraph he says:​

The case for reintroducing such a proposal is strong. We have to tax something, after all, and taxing soft drinks would let us reduce taxes now imposed on manifestly useful activities. At the federal level, for example, a tax on soda would permit a reduction in the payroll tax, which would encourage businesses to hire more workers.

​Yes, if we want public roads and schools, we do need to tax something.  But, I would have thought than an economist would argue that we'd want to tax things that create the least deadweight loss. And I would have thought there would be mention that we'd want taxes that are the least regressive (i.e., where the burden is not most heavily paid by the poor).

Maybe Frank is right and we should reduce payroll taxes, but how do we know soda taxes are the solution and are any less distortionary or are more progressive?  And why would soda taxes be the next best alternative to replace payroll taxes from an economic point of view?  Elsewhere, Frank has (very reasonably in my opinion) argued for across-the board consumption taxes in lieu of income taxes; so why now a soda-tax rather than an across-the-board consumption tax? There is no attempt to answer these important questions.     

Yet, he goes on in the concluding paragraph:​

Evidence suggests that the current high volume of soft-drink consumption has generated enormous social costs. So to those who have lobbied successfully against a soda tax, I pose a simple question: How do the benefits of your right to drink tax-free sodas outweigh the substantial costs of defending it?

​I disagree.  We don't know that soft-drink consumption per se has enormous social costs.  We have epidemiological-type studies/simulations based on correlations and assumptions but we don't know much from randomized controlled trials.  We also don't know that the costs (whatever they might be) are social rather than private.  As is well articulated in this article by Jay Bhattacharya and Neeraj Sood published in the Journal of Economic Perspectives when it comes to obesity more generally, the costs are primarily private​. Moreover, the expenses to Medicare and Medicare are really just transfers not deadweight loss.

Frank ends with a question: ​"How do the benefits of your right to drink tax-free sodas outweigh the substantial costs of defending it?"

First, I don't think most opponents of soda taxes would defend "tax free" but rather argue against special exceptions/taxes for one type of food vs another (because, among other reasons, the definition if "soda" isn't all that clear - and there are many substitutes for sodas that may be more calorie dense).  But, more generally, the answer is that the economic research shows soda taxes to have small effects on consumption, yet with large deadweight loss, and no meaningful impact on obesity.  The answer, in short, is that I defend my perspective using economic logic and the empirical results from economic studies.  I'm willing to be persuaded by new evidence or economic reasoning, but Frank didn't offer anything new.  I'm a bit surprised an economist of the caliber of Frank didn't meaningfully engage with economic evidence we do have.   

Do Small Reductions in Caloric Intake add up to Big Changes in Weight?

The answer is: probably not.​

​This is important question because there are many studies finding that various interventions (from fat taxes to menu labels) have very (though sometimes statistically significant) small effects on caloric intake.  Proponents of the policies are often undeterred - and say things like "well, a 20 kcal reduction every day can really add up to big weight loss over time."

As I've already discussed, some of this sort of analysis ​is based on the faulty logic that 3500kcal = 1lb.  But, as was mentioned in that post, our body does not react linearly to caloric changes in the fashion implied by this formula.  

Now, there's more on this topic by Trevor Butterworth in a well-written and catchy-titled post ​Sex And Lies! The Iffy Science Of Measuring Calories.  Here is a key excerpt:  

Hall was responsible for filling in the crucial measurements that elucidated one of the most widespread myths highlighted by Allison et al.: the idea that small, consistent changes in energy intake or expenditure will, over time, lead to large changes in weight. The assumption appears to have been based on the 1958 calculation by Max Wishnofsky that one pound of body fat gained or lost is equal to 3,500 kilocalories. This seemed to give people a convenient way to estimate weight loss through diet or exercise, while promising extremely convenient results. If you simply knocked off a 100 kilocalories from your energy intake each day—a ten-minute jog, or a mile walk—you'd end up losing over 50 pounds in five years. Little wonder that early proposals for soda and fat taxes promised to save Americans from themselves: pay a little more, consume a little less, watch a lot of weight disappear in a few years.
Hall first heard the claim listening to a dietician make a calculation for an obese patient. His intuition told him that this calculation was incorrect and would lead to exaggerated weight loss predictions. When he asked for a reference, he was pointed to a nutrition and dietetics textbook. "I subsequently found the mistake everywhere I looked." People weren't stopping to think "about the dynamic interaction between energy intake and expenditure, which is complicated," he says. What they failed to take into account was that "the rate of weight loss changes over time and is primarily determined by the imbalance between energy intake and expenditure—a value that also changes over time." To radically simplify his model, this means that cutting calories in your diet leads to a decreasing calorie expenditure, which in turn slows weight loss until weight eventually plateaus after a few years. "Of course," says Hall, "cheating on your diet will cause your weight to plateau much sooner." In the case of soda taxes, Hall and researchers at the US Department of Agriculture showed how static modeling overstated weight loss by 346 percent after five years.

Do People Want Calorie Labels on Menus?

On Tuesday evening, I was on air with Gil Gross who has a talk show on AM radio in San Francisco.  He wanted to talk about some research we recently published on menu-labeling.  I previously blogged about some of the results, but I wanted to re-mention something that came up during our talk.​

After discussing our finding that menus having only calorie information had no effect (they actually increased total calories ordered on average, though not significantly) and menus with a "traffic light" symbol had a small to moderate effect, the host asked whether people wanted these labels.  ​

Well, we actually asked precisely that question on a survey administered at the end of the meal.  ​Here is the exact phrasing of the question as it appeared on the 1-page survey.

menusurvey.JPG

We found 30.5% said they wanted a "menu with no nutritional information", 42% said they wanted a "menu with calorie contents of menu items listed", and only 27.5% said they wanted a "menu with a symbol to represent the calorie content of menu items."  ​

​So, curiously, the most popular option is the one that had zero effect (and if anything increased total calories).  The menu which actually lowered caloric intake was actually least preferred.  

On a last note, people sometimes take these kinds of survey questions to indicate what a business (or government) should do.​  That's not the right interpretation.  Just because consumers say they want labels doesn't mean it's good business (or good public policy) to provide them.  Labels cost money (and might change behavior in ways that cost money) that must be weighed against any benefits they provide.  Moreover, if consumers really want these labels, won't they frequent restaurants who voluntarily provide them?  Thus, there seems to be a clear incentive here for restaurants to provide the labels if they are truly demanded - and indeed many restaurants voluntarily do it already.  

Does Sugar Cause Death? Or Increase Life?

All over the news today I've read about some research that was presented by some Harvard professors purporting to show that sugary beverages lead to 180,000 deaths worldwide and 25,000 deaths in the US (here is Time, ABC,  ​Forbes, or a press release by the American Heart Association).

​I haven't yet been able to get my hands on a copy of the actual paper (which isn't yet published) but from all accounts, this is not hypothesis-testing-science sort of research but rather assumption-driven-simulation sort of research.  I've done some of that kind of work myself and it can produce some useful insights, but the results are only as good as the assumptions, and I suspect (though don't know) the simulation is assuming causality where there is only correlation.

While we are looking at correlations, we might as well have some fun with it.  About two weeks ago, I blogged about (and reanalyzed data from) some research by anti-sugar crusader Robert Lustig that was published in PLoS ONE.  In short, they showed a positive correlation between countries that eat a lot of sugar and prevalence of diabetes in the country.  The correlation was widely interpreted as proving a causal link between sugar and diabetes.  So, let's apply that same logic to the topic of death and sugar consumption.

I took the same sugar consumption data as I talked about in my previous post​.   Then, I merged it with life expectancy by country as compiled by the UN (you can download the data from Wikipedia).  Here is the relationship between average life expectancy in a country (in years) and per capita availability of sugar (in kcal).

sugarlife.JPG

We've clearly got a positive correlation here.  In fact if I run a population-weighted regression, I find that for every 100 kcal increase in sugar availability, life expectancy increases 1.9 years!  The p-value is even less than 0.001!​  Drink more sugar and you'll live longer!

Now, do I actually think increased sugar consumption increases life expectancy?  Probably not.  Richer countries can probably afford to buy lots of things (like more sugar) and richer countries are also likely to have higher life expectancies (because they can also buy more health care).  But, it does make you wonder what's going on if the Harvard researchers are right and all that sugar is causing so many deaths. ​

I rather suspect, a lot of deaths due to other problems are being attributed to sugar from sodas.  I'm reminded of this passage from Eric Oliver's book Fat Politics as it relates to attributing deaths (or medical costs) to obesity.

The researchers who estimated that obesity costs us 100 million dollars a year did so by calculating all the expenses associated with treating type 2 diabetes, coronary heart disease, hypertension, gallbladder disease, and cancer . . . Once again, they simply assumed that if you got heart disease or breast-cancer it was because you were fat.

Obesity and Age among Women

I was looking through some data on how people's weight has changed over time in this CDC publication.  I have been curious how researchers calculate age adjusted measures, so I wanted to delve into it a bit myself.  

Here is an excerpt of the data for women from Table 6 in the CDC report.

weightbyage.JPG

It is apparent that weight has increased in every age range from the 1960-1962 time period (which I've called 1960) to 1999-2002 (which I've called 2000).  It is also apparent that the age distribution has shifted, with a larger share of older women in 2000 than in 1960 (I'm assuming the sample sizes in these data are consistent with population statistics on age).  So far, none of that is news.  So, let's dig a little deeper.

The mean body weight of women in the US in 1960 can be calculated by multiplying the weight of women in each age range by the % of women in each age range and summing across all age ranges.  When I do that, I find that the average weight of women in 1960 was 140.05 lbs.  

Now, for a little thought thought experiment.  What if we took the body weights by age observed in 1960 but instead assumed that we had the (older) age distribution that existed in 2000.   ​To calculate this "strange" age-adjusted average, I multiply the weight of women in each age range in 1960 by the % in each age range in 2000 and sum across all age ranges.  The result is 141.2 lbs.  The difference is 1.15 lbs.

What does this mean?  If the female population were, as a whole, older in 1960 - as it is today - then the average weight for women back then would have been 1.15 lbs higher.  ​As a result, a small part of the weight gain from 1960 to 2000 (about 1.15 lbs worth) is due to changing age structure rather than weight gain per se.  

The other thing I noticed is that it matters how you do the age adjustment.  If I use the 1960 age distribution as the "base" then the age-adjusted weight gain from 1960-2000 is 24.1 lbs.  However, if I use the 2000 age distribution as the "base" then the age-adjusted weight gain from 1960-2000 is "only" 23.1 lbs.  Thus, we can push our weight gain figure up or down a pound simply by choosing which base we wish to use.  

It is interesting to note that weight gains have been highest among the youngest females and lowest among the oldest.  The gain in weight from 1960 to 2000 for 20-29 year olds was 28.8 lbs but the gain for 60-74 year olds was only 17.4 lbs.  Also, the variation across years has changed a lot.  In 1960, the difference in 20-29 year olds and 60-74 year olds was 19.6 lbs.  Today, that same difference is only 8.2 lbs.  So, we are fatter but more equal?    

Regardless of what has happened to weight, I can't help but think that it is a very good thing that we have more older women in 2000 than 1960.  Sure, they're a little fatter, but probably thankful to still be kicking.  ​

P.S.  It is important to note that the gains from 1960 to 2000 have, in the recent decade, leveled off and there does not appear to be much change in obesity prevalence among women in the past 10 years (see this paper in the Journal of the American Medical Association or my previous blog post).​