New Research on the Berkeley Soda Tax

You may remember the discussion surrounding a research paper released back in August that used interviews and survey data to suggest that the tax on sodas that went into place in Berkeley caused a significant reduction in soda consumption.  

As several other locales are considering new soda taxes in the upcoming election season, this sort of research is valuable in trying to sort out the potential effects of the policies.  

Now there is new research by Scott Kaplan, Rebecca Taylor, and Sofia Villas-Boas at UC Berkely.  The authors utilize a dataset on retail sales of various drinks in dining locations at "a large university" - presumably Berkeley.  Importantly, the authors do not actually look at the effect of the implementation of the tax, but rather they look at what happened to soda sales because of the publicity and information surrounding the vote.  That is, they look at soda sales surrounding the time of the vote but before the tax actually went into place.

Here is a figure from the paper summarizing the main findings: 

The authors write:

“We find a 30% drop in soda sales relative to other product groups during the post-election
period. In a related and contemporaneous study using survey data, Falbe et al. (2016) find
an average 21% drop in SSB quantity sold. However, because the surveys were completed
only before the election and after the tax implementation, Falbe et al. (2016) are unable to
distinguish whether this effect was from the campaign and election or from the tax itself.
Our results show that soda sales fell on-campus after the soda tax election yet before prices
changed due to the tax. This suggests that comparing pre-campaign to post-implementation
consumption may confound a tax effect with an information effect. This has important
implications for external validity. If the Berkeley SSB tax is replicated elsewhere without
a proceeding campaign war and affirmative election outcome, its effects on consumption
may differ substantially. In other words, given the amount of money spent in the Berkeley
campaign on each side of the battle, it is important to understand how much behavioral
change was due to the election and how much was due to the tax itself.”

My take on the results is that these soda tax policies may well have sizable "signaling" or "information" effects aside from whatever pecuniary effects exist.  I have found similar results related to animal welfare regulations: that the publicity surrounding a vote has a significant impact on what people buy aside from whatever impacts the policy actually has on the price or foods offered.  In short: information dissemination campaigns may be as important or more important than taxes or bans on products.  In my assessment, information policies are often far more justifiable than are more coercive policies that restrict choice. 

It will be interesting to see as future research emerges whether and how the actual implementation of the tax changes soda consumption and how long lasting are these information effects.  

More on soda taxes

A few days ago, the World Health Organization (WHO) came out with report, suggesting the use of food taxes and subsidies to encourage healthy eating.  They were particularly in favor of soda taxes.  Soda taxes seems to be picking up steam in the U.S..  After passage in Berkeley, they will now be on the ballot in several locales in coming weeks.  

I've written so much on these topics, it's hard to know what more to say.  So, I thought I'd just, for the record, tell you what I had to say on a recent Food Sommelier podcast when the host asked me about this topic (and revealed her support for soda taxes, which came about in part because she said she felt guilty for having worked for PepsiCo earlier in her career).  

I'm in episode 38 and the discussion on soda taxes starts at about the 20 minute mark.  Here is my lightly edited discussion on the issue. 

“I’m not a fan of soda taxes for a whole host of reasons . . . but let me first say, though, that it’s really not that big a deal.  And that’s probably one of the reasons I’m against it . . .  As much as I’ve written about it, you’d think I’d get my feathers ruffled a lot [over things like the Philadelphia soda tax], but I don’t have a dog in the fight really one way or the other.  It’s not a big deal in the sense that, number 1, it’s just not going to have much of an effect on obesity rates if you look at the best available research.  We are talking about taxes that will have very, very small effects on people’s weight, and there a lot of reasons for that.  

There are substitutes for sugar sweetened beverages.  People can switch to juices or even non-beverage alternatives that may have calories in them.  I’ve seen a number of studies that suggest that.  Just because we put a tax on something doesn’t mean people are not going to consume calories; they might instead switch to something else equally caloric.  . . . 

We have these intuitions . . . and little thumb rules like for every 3,500 kcal we cut out, we lose a pound.  The reality is that relationship is not linear at all.  It’s nonlinear . . .  When we’re thinking in a linear way, each calorie I cut out will cause a constant reduction in weight, but it doesn’t really happen that way.  There are diminishing returns.  You may lose a little bit initially but then it will really level off.  . . .

When you look at the burden of the tax, and this is really true of almost any food tax, its going to tend to be borne relatively (at least relative to income) more by people in the lower economic strata of society.  The reason for that is that if you look at the share of spending on food, it tends to go down as we make more money.  What that means is that poor people are spending a larger proportion of their income on food. So, anything we do to make food more expensive, that burden or that tax, is going to tend to fall more heavily on lower income populations. . . .

I’ve got a paper actually coming out . . . where we compare very low income to regular income consumers.  What we tended to find there is that is that, especially in the case of subsidizing healthy foods, the richer consumers benefit the most because they’re already, first of all, consuming relatively health foods.  And, because we found . . . that the poor tended to want to stick to their original diets. They were more habit prone, so they didn’t change quite as much either when it was a tax . . . or a subsidy trying to get them to eat something a little healthier.  

I would say lastly, I’m going to bring up this sort of elitism. . . . This sort of paternalism argument.  We feel like we know how other people should be eating.  . . . I think it’s really hard to put ourselves in the shoes of other people, and so for us to take a step back and say ‘you should be doing something different; you should be eating more like me’ presumes that we know what it’s like to have their life and have their kind of income and know all the other sorts of things they’re facing. . . .  I have a problem philosophically with that. . . .

And I do think it’s different than . . . cigarette taxes.  With cigarette taxes there really was this externality – the second hand smoke.  When you’re smoking, that really does have an effect on the people around you.  With the drinking of soda, it’s really less clear there’s that same kind of phenomenon at play.  Most of what’s happening here is some kind of redistribution within our healthcare system because of Medicare and Medicaid.  But, that’s much more complicated than most people realize.  Most of what’s happening here are subsidies flowing from relatively wealthy people to relatively poor people because relatively wealthy people pay more in taxes. . . . It’s not a popular solution but part of the argument is that if people know their health care expenses are going to be taken care of, they’re going to eat in an unhealthy way . . . Economists call that a moral hazard.  The answer for a moral hazard is that people need to have some skin in the game.  We need people to pay a little bit of the costs of their health care.  It doesn’t have to be the same for everybody, and maybe it’s just a small amount for people who don’t have much income, but I think if the concern is that if people are going to behave “irresponsibly”, there needs to be a bit of a price for that in terms of their health care costs.  But, of course, there is a real price for being obese.  That’s something we tend to forget – that there is a lot of social shame associated with being obese, wages can be lower especially for women, and there are all the attendant medical costs, some of which are shielded from the consumer because of our health care system but a lot of those are borne directly.  There is a real cost to being overweight and obese, and people bear a lot of that just through their own daily lives.  

I’m running on here, but one last point that is really important because I hear so many people get this wrong.  What they say is, ‘well our farm policy system subsidizes food and makes sugar cheaper.’  That is absolutely false.  I’m not a fan of farm subsidies, but that particular argument is false for two reasons.  One is that if you look at cane sugar.  Cane sugar has a set of really convoluted policies, but they essentially restrict supply. . . . What [sugar producers via policy] are able to do is keep out foreign competition and keep other producers from growing sugar cane.  . . . World sugar prices are much higher than they would be if we didn’t have our US cane sugar policies.  The other thing is high fructose corn syrup (HFCS).  Right now roughly 40% of our corn supply goes to ethanol.  Ten years ago, that was mostly going to livestock and food processing. . . .  It’s not exactly a farm policy, but the energy policies we’ve had over the past 10-20 years have dramatically shifted corn production from going to places like HFCS to instead ethanol production and our cars, and as a result has made HFCS more expensive than it would be otherwise.  

Should we tax sugar?  In some ways, we already do, it’s just not very transparent that we’re doing it."                                       

Berkeley Soda Tax

There have been a number of news stories about this new paper in the American Journal of Public Health that studied the impact of Berkeley's new sugar-sweetened beverage tax (aka "soda tax").  The authors surveyed residents of Berkeley before and after the implementation of the tax and asked about beverage consumption.  They also surveyed people in Oakland and San Francisco (who were presumably not affected by the tax) before and after the tax.  By comparing these two groups before and after, the authors can calculate something like a difference-in-difference estimate of the impact of the tax.

What did they find?

“Consumption of SSBs decreased 21% in Berkeley and increased 4% in comparison cities (P = .046). Water consumption increased more in Berkeley (+63%) than in comparison cities (+19%; P < .01).”

The results have been largely heralded as indicating that the taxes "work".  Here is a bit from the organization Healthy Food America:

“this study provides another key piece of evidence that sugary drink taxes work, not just to raise revenue for important community priorities, but also to reduce consumption and shift sales from an unhealthy product to healthier drinks, such as bottled water,” said Jim Krieger, MD, MPH, executive director of Healthy Food America. “As four other communities consider their own taxes this fall, the Berkeley findings join those from Mexico and elsewhere to show that sugary drink taxes have great benefits – especially in low income communities.””

We shouldn't be too surprised that a tax reduces consumption - more confirmation that the demand curve slopes downward.  Yay Econ 101!  The real question about soda taxes hasn't been "whether" but "how much" consumption falls when prices rise.  

First, I'll touch on some conceptual issue related to the interpretation of the study then offer a few thoughts on the study methods.  

As indicated, I've seen numerous studies showing that this paper "proves" that soda taxes "work."  I'm not sure what "work" means.  There have been scores of studies projecting impacts of soda taxes, and virtually all suggest the taxes will lower soda consumption by some amount (though curiously the evidence is much less clear if you look at studies that have looked at actual sales data before and after taxes).  But the goal isn't to reduce soda consumption for the sake of reducing soda consumption.  The goal, presumably, is to make people's lives better - to reduce obesity or other dietary related diseases.  On this front, the evidence is much less clear that soda taxes will have a substantive effect on body weight.  Moreover, as other studies have shown, we need to be cognizant of what people eat and drink instead when they substitute away from higher-priced soda, and many of these options could have adverse health impacts as well.

The largest conceptual issue in all this is whether a tax can actually make people better off.  Yes, a tax can reduce consumption.  But, does that mean people are happier?  Even if people switch to a lower-priced alternative after a tax, it doesn't follow that they're necessarily better off.  After all, consumers could have chosen the lower-priced alternative before the tax if that's what they really preferred.  Thus, the tax causes people to choose a lesser-preferred option.  This is a standard economic result: consumer welfare falls when prices rise.  Here's what I wrote in a piece for the Canadian Journal of Diabetes. 

“More fundamentally, one must ask what conceptual basis is being used to assert that SSB taxes will increase consumers’ welfare? Presumably, some consumers already consider health impacts when they choose what to eat and drink. More generally, taxing food or SSBs is analogous to reducing consumers’ real income, which almost certainly harms the consumers (9). Perhaps consumers suffer from lack of information or other cognitive biases, but even so, Lusk and Schroeter (10) show that only in very limited cases would a tax increase consumers’ long-term welfare. Sugden (11) further points out the philosophical (not to mention political) problems encountered when attempting to base public policy on the presumption of consumers’ behavioural biases. In particular, asserting that someone else consumes “too much” SSBs presumes that the nutrition expert or politician knows better which factors most impact an individual’s ultimate well being than the individual herself or himself. Such paternalism may be justifiable in the case of children or the mentally impaired, but it is less compelling when considering the general population. It is likely the case that excess consumption of SSBs will lead to health problems; however, people care about tasty, satisfying foods and beverages in addition to health. Life is full of difficult tradeoffs, and it is conceptually problematic for a third party to deem another person’s choices wrong or incorrect, given that different people have different preferences, incomes and constraints (assuming that people are making decisions with accurate information about the risks they face). If the argument is that people do not understand the risks of SSBs, then the appropriate policy response is information provision, not a tax.”

I went on to tackle the argument that rising public health care costs justify the tax, but I won't belabor the point: showing a tax "work" involves much more than showing that it reduces consumption.  

Now on to the Berkeley study's methods.  Overall, this is a nicely designed study that uses a difference-in-difference approach to try to tease out a causal effect.  My biggest beef with the study is that it relies on consumers' stated consumption behaviors.   The Berkeley tax has been a high profile event, and no doubt many Berkeley residents were aware of the debate and policy change.  It is possible that what we're picking up is some form of social desirability bias: Berkeley residents know they and their neighbors passed a tax on soda, and now here's this researcher asking about soda consumption.  The social pressure is clear: I don't want to be the kind of person who consumes the product everyone else wants to tax.  I don't want to look like some kind of social outcast, so I'm going to hedge and give a lower level of consumption than I actually consume.  

Why didn't the authors do this study using scanner data based on actual grocery sales?  These data are easily attainable from companies like Nielsen and IRI and can't be much more expensive than the surveys the authors conducted.  Even still, there would be other questions about the longevity of the effect, the substitution toward other food and beverages after the tax, the degree of substitution across city boundaries, and so on.

All that said, I'm more than willing to accept the finding that the Berkeley city soda tax caused soda consumption to fall.  The much more difficult question is: are Berkeley residents better off?  

Zhen et al. on Soda Taxes

Yesterday, I was browsing recent back issues of the American Journal of Agricultural Economics looking for papers on consumer demand (somebody has an AAEA presidential address to write).  

I came across two papers by Chen Zhen and co-authors published in 2014 on effects of sugared sweetened beverage taxes (or "soda taxes") that I'd previously read but not blogged on before.  I thought I'd mention them here given the ongoing policy discussions surrounding the issue (Philadelphia politicians are currently considering a soda tax; Oakland has a ballot measure planned on the issue; and there is much debate about the potential effects of the soda tax already passed in Mexico).

In the first paper, Zhen and colleagues show that the way most of these taxes are designed, on a per ounce of soda basis, is not nearly as effective as would be a tax on a per calorie basis.  The authors write:

“For every 3,500 beverage calories reduced, the estimated consumer surplus loss due to a calorie-based tax is $1.40 lower than the loss induced by an ounce-based tax. A 0.04 cent per kcal SSB tax is predicted to reduce beverage energy from ScanTrack supermarkets by 9.3%, compared with 8.6% from a half-cent per ounce tax. Applying this percentage change to beverages obtained from all sources, we calculated that a 0.04 cent per kcal tax on SSBs will reduce total beverage energy by about 5,800 kcal per capita per year.14 Compared with an ounce-based SSB tax that also achieves a 5,800 kcal reduction in beverage energy, the 0.04 cent per kcal SSB tax is estimated to save $2.35 per capita or $736 million for the U.S. population in consumer surplus per year.”

The "lost consumer surplus" means consumers are worse off with either tax.  This is an issue I've raised several times before: there have been few serious attempts to carefully articulate how a soda tax improves consumer welfare given that consumers don't like paying higher prices (e.g., see here or here).

In the second paper, the authors show how a sugar-sweetened beverage tax might have unintended consequences. 

“The preferred demand specification predicts that almost half of the reduction in SSB calories caused by an increase in SSB prices is compensated for by an increase in calories from other foods. We further found potential unintended consequences of an SSB price increase on sodium and fat intake. Because energy intake is just one of many dimensions of nutrition, the results on sodium and fat highlight the complexity of using targeted food and beverage taxes to improve nutrition outcomes.”

They predict that one half-cent per ounce tax on such beverages would reduce body weight by "0.37 and 0.16 kg/person in 1 year and 0.70 and 0.31 kg/person in 10 years for low- and high-income adults, respectively."

They also write:

“The welfare loss for low-income households is about $5 per household per year more than high-income households because low-income households reported higher SSB purchases in Homescan. This difference in welfare loss between low- and high-income households reinforces the regressive nature of an SSB tax”

Cost Effectiveness of Soda Taxes

In a piece for Cato, Christopher Snowden discusses the effectiveness (or lack thereof) of soda taxes that seem to be gaining traction worldwide.  Snowden's views closely mirror my own.  I like the way he framed the relative effectiveness of soda taxes in this passage:

“Whilst the benefit remains forever on the horizon, the cost can be easily calculated; it is simply the amount of money squeezed from consumers by the tax. In New Zealand, for example, advocates claim that a 20 per cent tax on soda would save 67 lives per year and raise $40 million (NZ).[12] Leaving aside the reliability of the New Zealand forecast, this works out as a cost of $600,000 (NZ) for every life that is extended and does not represent good value for money.

Political action on public health grounds is often justified by the costs of unhealthy lifestyles to the healthcare system, and therefore to the taxpayer. The economic costs of obesity are often misrepresented and fail to account for savings to taxpayers, but even if they were more reliable it is far from obvious that additional taxes would relieve the economic burden.[13] For example, the UK’s Children’s Food Campaign recently claimed that a 20 per cent tax on sugary drinks would reduce healthcare costs in London by £39 million over twenty years, but their own figures suggest that the tax itself will relieve Londoners of £2.6 billion over the same period.[14] The cost of the tax will therefore exceed the savings by several orders of magnitude.”

By the way, if you want to see which (out of more than 100) action will produce the biggest bank for your buck, check out the work of the Copenhagen Consensus, which routinely conducts cost-benefit analysis on a whole set of issues.  See their list for the most cost-effective actions.