Are there “food deserts” as a dietary problem?

by on April 4, 2013 at 2:22 pm in Food and Drink | Permalink

Via Jacob A. Geller, the evidence is now in and it seems to suggest no, food deserts are not a real problem:

Here is more, and here is the study itself.  If you look at the statistical tables, they’re pretty striking.  Even where there is statistical significance — which is the exception to the rule — the size of the effect is so tiny, it’s like practically nothing.  For example, on the margin, adding one full-service supermarket within a one-mile radius of your house is associated with an average BMI decrease in your neighborhood of .115.  That is a difference of just one pound.  (see back-of-the-envelope calculations here)

So there is really no relationship, according to this one recent study of nearly 100,000 Californians, between the distance between your body and a full-service supermarket (or any other kind of food store), and whether or not you are obese.  Distance, which is a proxy for access (the idea of a food desert is that the nearest supermarket, which has fresh produce, is distant), is for all practical purposes a non-factor.

Here is a good example:

For example, when you last ordered food at McDonald’s, did you even notice those ten salads on the menu?  Did you order them?  No, and me neither.  And did you ask for a cup of water, which is free, instead of a soda?  No again.  (That’s my experience anyway, and that of millions of other Americans)

And an excellent parallel:

And what’s interesting from a political standpoint, is that this analysis similarly applies to drugs — tackling the supply side does little for heroin addicts, for example, increases the price of heroin, which induces supply to come back into line with the addicts’ inelastic demand curve — and yet most liberals would probably agree with me that drug addiction ought to be tackled on the demand side (spending money to convince young people not to shoot up heroin for example, instead of spending money on patrolling the border), but the same liberals who agree with this analysis of the drug war will often turn around and favor unproven supply-side solutions to obesity like subsidizing supermarkets in low-income neighborhoods, despite the absence of evidence to support those ideas.  Note that libertarians are more consistent on those issues — they oppose supply-side interventions in most, if not all, illicit drug markets, and also oppose supply-side interventions into food markets.

lemmy caution April 4, 2013 at 2:36 pm

Sugar water is less addictive than heroin. Pretty sure a soda ban would be effective, if overly drastic.

TYD April 4, 2013 at 2:44 pm

May as well ban coffee too

j r April 4, 2013 at 4:18 pm

Soda is carbonated water and syrup. You really think that those items can’t be easily gotten by anyone who wants them?

Hasdrubal April 4, 2013 at 4:55 pm

What would replace pop? Would it have better or worse health effects? For example, most juices on the market have just as much high fructose corn syrup in them as pop does. Diet pop is arguably just as bad for your health as regular, but in different ways. Water? It’s already free at the margin, yet it can’t outcompete pop, why would it suddenly become a substitute?

Yancey Ward April 4, 2013 at 5:43 pm

I picked the wrong week to give up Pepsi.

Jacob AG April 4, 2013 at 9:48 pm

That’s true, *if* it’s an actual soda ban and it’s well-enforced. If that is a reference to the Bloomberg ban, then it’s not really a ban, because people can simply buy more, smaller sodas if they want to.

And this is speculative, but it is actually *possible* for a ban on certain sizes of drinks to result in certain people drinking more sugar-water than they otherwise would have. For example I could drink 16oz and not be satisfied, and buy a second 16oz drink, and end up drinking more than 24 oz, which is what I *might* have drank if 24oz drinks were legal.

If you see any studies in future looking at the impact of Bloomberg-style soda bans and finding no change, consider this as a hypothesis.

Jacob AG April 13, 2013 at 6:33 pm

UPDATE: Such a study has now been completed: http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0061081

From the study (which only had 100 observations, all of them undergraduate students, caveat emptor): “Our research suggests that businesses have a strong incentive to offer bundles of soda when drink size is limited. Restricting larger-sized drinks may have the unintended consequence of increasing soda consumption rather than decreasing it.”

bjssp April 4, 2013 at 2:39 pm

Wouldn’t both things–availability of certain types of food, both in general and depending on price, as well as nudges to make people eat certain types of food over others–go hand in hand?

Also, what about this>?

“This study has several limitations. First, we measured food outlet type, not the availability of certain foods. We obtained food outlet data from InfoUSA; business listings are rarely up-to-date or without error. One study reported only fair agreement between commercial data and field observations for supermarkets, grocery stores, convenience stores, and full-service restaurants and poor agreement for fast-food restaurants (19). The dietary intake questions we used did not provide guidance on serving size, and they asked about a small number of food items; hence, they did not allow examination of overall diet quality. The questions also had a long recall period of 1 month. BMI was calculated from self-reported height and weight; self-report tends to underestimate BMI (20–22). The study used data from California, and the results may not apply to other geographic regions or populations. Finally, this study used cross-sectional data and was unable to establish causation.”

prognostication April 4, 2013 at 5:30 pm

Yeah, as usual, the reality is much more nuanced than “definitely an issue” or “definitely not an issue.” I know of work that has shown that if you ground truth InfoUSA and D&B as data sources for this type of research, it is not super accurate.

To say nothing of the obvious geographical critique, which is that scale and place matter, which is something that most economists generally would prefer to ignore.

bjssp April 4, 2013 at 9:24 pm

If you go to this guy’s blog, you’ll see a long (and, I should add, thoughtful) post on this topic, which links to a Mark Bittman opinion piece on whether it costs more to eat a healthy diet than it does to eat crap like fast food. I’ll assume Bittman didn’t stack the deck too much and that there are legitimately easy ways to get a cheap but healthy meal. The question is, what’s the availability of food, specifically in areas where obesity is a problem, which in a place like NYC would probably be poorer and/or minority neighborhoods? It’s not that there’s no place to get food, only that, if my impression is accurate, there just aren’t that many places with a wide enough selection outside many of the wealthier, trendy neighborhoods.

Of course, I could be wrong, but gut instinct tells me that this is, in some way, part of the problem. I’d also question the compounding effect over time of adding a pound (or two) over the course of many years.

Sigivald April 5, 2013 at 4:01 pm

The problem is not “healthy food is too expensive”, as far as I understand it.

It’s that the “crap” (I pointedly do not endorse that value judgment) is more appealing, and less work… and you don’t have to have any cooking skills or capital in order to consume it.

I also don’t think there’s “a problem” here, at least not one in the State domain.

Floccina April 8, 2013 at 10:24 am

You do not need cooking skills to eat a carrot, an orange or a banana and they are all cheap. Cabbage can be eaten raw no cooking and very cheap not to mention greens (I love raw spinach). There are lots of foods that you would call health and are cheap and can be eaten raw. The premise is just wrong.

Fiyrdkyfkugckhg April 5, 2013 at 12:13 am

Is the evidence used here any better then the evidence used in allocating $340,000,000 to solving food deserts?

Tom T. April 5, 2013 at 10:14 am

That’s what I was thinking. These cited limitations suggest that no one discussing food availability really knows what he or she is talking about.

Jacob AG April 4, 2013 at 9:43 pm

This is an excellent point, and the relationship between obesity and the availability of foods deserves to be studied. But the idea of food deserts is often presented not as a lack of availability of healthy foods per se, but as a lack of availability of healthy foods for a specific reason, namely that full-service supermarkets are very distant. Hence this is a study about that particular notion of food deserts.

Although I should reiterate that even if a relationship between obesity and the availability of certain types of foods could be shown, that would not tell you about what was causing obesity — supply or demand.

Rahul April 4, 2013 at 2:46 pm

I do both pretty often: Get a McD Salad as well as a cup for water.

The Salad’s are pretty good and quite large actually. The dressings are not bad either. Nothing fancy, but definitely value for money.

BC April 4, 2013 at 7:19 pm

I often get the McD’s salads too, which makes it hard for me to interpret the presence of a McDonald’s instead of a supermarket in an area as pushing or nudging people into fatty foods.

Benny Lava April 4, 2013 at 2:47 pm

A lot of the talk about food deserts was myths invented by lazy or stupid journalists and professors.

http://www.urbanophile.com/2011/01/25/yes-there-are-grocery-stores-in-detroit-by-james-griffioen/

JWatts April 4, 2013 at 4:09 pm
zbicyclist April 4, 2013 at 4:13 pm

Yes, there’s that. There’s also the issue that stores stock what people want to buy. If there is a shortage of vegetables in certain urban areas, in those same areas there is no shortage of liquor stores and of lottery ticket outlets.

I don’t think you have to be Steve Sailor to see there’s political correctness in blaming the supply side.

Hazel Meade April 4, 2013 at 4:34 pm

“Food deserts” were a myth invented by progressives who wanted to find a way to blame obesity on capitalism instead of poor people’s dietary habits.

There are a lot of people who find “blaming the victim” highly uncomfortable. You can’t blame fat people for being fat. They are victims of a disorder, either a medical one or a social one. The bad dietary habits of Western culture have been imposed upon them, the capitalist system doesn’t provide them with healthy dietary choices, whatever. Anything but say that they are fat because they choose to eat pizza and french fries and drink sudary sodas of their own free will. No, they have to be denied agency and an external source must be found. “Food deserts” implicate a target that is familiar and easy from a progressive standpoint: capitalism. Just blame capitalism, cause that way you don’t have to blame an actual person.

FC April 4, 2013 at 5:48 pm

It became clear in the 1990s that people in wealthy countries were cut down on drinking, smoking and shooting each other. So professional activists came up with “food deserts” to see them through to retirement.

BC April 4, 2013 at 7:28 pm

It’s not even clear that fat people are viewed as victims. It’s more like a disagreement with the choices that fat people make. Progressives know that they can’t just advocate taking away fat people’s freedom directly, so instead they invent a rationalization in which they’re actually “helping” fat people by taking away their choices.

bjssp April 4, 2013 at 9:34 pm

This is the funniest thing I’ve read in days!

So Much For Subtlety April 4, 2013 at 11:34 pm

It is also a way of blaming poor people and minorities. You can’t say that a lot of Black people make bad choices. You can’t say that some Hispanics are idiots. You can’t say that the poor inflict many of their problems on themselves. But you can say that Fat people, ie the poor, Blacks and Hispanics, are aesthetically unpleasing and need well meaning Upper Middle Class liberals (ie Whites) to run their lives for them.

Sigivald April 5, 2013 at 4:02 pm

Exactly. A way to convert “eww, fat people are GROSS” into something acceptable and something to Fix.

Ricardo April 5, 2013 at 1:24 am

The supposed relationship between poverty and obesity is mostly a myth. Obesity rates among women decline with household income but it’s still the case that 29% of women in solid middle class households are obese compared to 42% of women in poorer households. Among men, there isn’t any single statistically or numerically significant relationship. Among black men, obesity increases with income.

KLO April 5, 2013 at 2:07 pm

The data are interesting and I have relied upon this to draw the same conclusion, but I would also point out that the data are not very granular. The study relies on the three income bands only, with the highest income group threshold being 350% of the FPL, which, in 2008, meant that a family of 4 with household income above $77,000. If people in the top 5% of incomes were less likely to be obese, we would not know it from this data.

Hazel Meade April 5, 2013 at 3:58 pm

That would appear to further undercut the “food desert” theory, since the basic idea is that the food deserts coincide with economically depressed areas. Nobody’s arguing that a lack of access to grocery stores causes middle-class black men to get fat.

Floccina April 8, 2013 at 10:58 am

Also fat people have a harder time finding high paying work.

Bill Christens-Barry April 4, 2013 at 2:50 pm

Parallel, what parallel? Umm, does the difference in the legal framework surrounding both supply and demand between foods and drugs bear any thought here? Does the difference between legal and economic support for one indicate some degree of orthogonality? And is this a demand side or supply side distinction, or both?

On the topic of the hallmark of small minds: consistency would seem to demand that school lunch programs serve high fat, high cholesterol red meat, fresh green vegetables, and heroin.

Let’s be more critical in our thinking here, please.

Jacob AG April 5, 2013 at 8:52 am

On school lunches, I actually argue at the bottom of my post that children are a case where supply-side interventions are appropriate, simply because children do not have demand curves and/or their curves don’t matter very much. Everything they eat is given to them by a 3rd party. It’s like everything they consume is an externality. So you might as well give them something healthy.

But adults *do* have demand curves, and I’m hypothesizing that they are inelastic. Adults are very different from children in that a) they have demand curves and b) that actually matters. So that would imply different policies for one than for the other.

Also, I’m not sure if your high fat, high cholesterol, red meat and fresh green vegetables is supposed to be healthy or unhealthy. The conventional wisdom is that aside from the vegetables that would be unhealthy, but there are serious scholars like Gary Taube who argue that that is like the Platonic ideal of a good meal. (But I don’t know if that’s what you were suggesting…)

nw April 5, 2013 at 6:23 pm

Um, have you ever known any children? And what was your apparent age
when you were manufactured?

mavery April 4, 2013 at 3:06 pm

Two things:

1) The premise of physical distance to a supermarket being a proxy for availability of “healthy” isn’t particularly convincing for a number of reasons.
2) The drug analogy seems pretty flawed, given both that healthy eating advocates do like policies that teach/espouse healthy eating (ie, they do like the supply-side solutions as well) and that the demand curves look quite a bit different for drugs than for hamburgers.

Fast food and drugs: the new guns and alcohol.

Hasdrubal\ April 4, 2013 at 5:10 pm

I can empathise with distance to a supermarket equating with healthy food options: It’s a pain and kind of embarrassing to bring home bags of groceries on the bus. Personal experience made the initial idea plausible to me, if we’re talking about low income people. At least it’s worth investigating.

On the other hand, it’s not really surprising that ease of shopping is probably pretty far down on the list of reasons to not eat healthily. Cooking at home is enough of a hassle and takes enough time (cooking may be quick, but there’s still cleaning those stupid dishes, and the counter, and the TV tray that I ate on, and why do I have to wait 45 minutes to eat when I’m hungry now, and I just want to kick it on the couch and unwind from a day of work, and Oh My God how do people with kids handle this?) and up front investment, (pans, spices, why do I have to buy a 16oz can of coconut milk when the recipe calls for 2tbsp?) It wouldn’t take much to convince me that food deserts don’t have a noticeable impact on eating habits.

Mike April 4, 2013 at 9:46 pm

It may not take much, but it’d be nice if some of it was data.

chug April 4, 2013 at 3:13 pm
Justin April 4, 2013 at 3:23 pm

On the McDonald’s front, I lost 40 pounds and I loved eating at fast food restaurants because it was one of the few times you could get an accurate calorie count. Grilled Chicken Classic: 420 calories. McDouble: 390 calories.

MD April 4, 2013 at 5:17 pm

Once I saw the number of calories in all that stuff, I lost my appetite for fast food.

ad*m April 4, 2013 at 5:52 pm

Do you even know what your latte and parfait count up to?

MD April 5, 2013 at 1:15 am

My what and my what? I don’t eat/drink that stuff, but if I did go to Starbucks to get them, I would know. (I don’t know if all Starbucks post that stuff, or if they post that stuff bc California makes them)

Zephyrus April 4, 2013 at 6:52 pm

It’s really disgusting–a chicken sandwich having 500 calories? UGH!

I’m going to stick to my Chipotle burrito, which is organic and healthy.

Deman April 4, 2013 at 7:49 pm

I am not sure if this works for everyone but I have KFC every day for lunch – A full meal with Diet Soda (Wings+Burger+Chips+Gravy) is around 1300 calories. But that is my only meal of the day besides a small brekkie (single slice of bread with cheese approx 100 calorie) and 2-3 scotches in the evening (150 Calories). I am losing weight on this diet. On weekends I make up the lost weight. I am a pretty healthy 30 yr (74 Kgs, 5’11).

Jan April 4, 2013 at 9:53 pm

SA or Netherlands?

Deman April 4, 2013 at 10:15 pm

Me? Australia..

Urso April 5, 2013 at 9:34 am

I guessed Australia. Sunglasses are “sunnies,” kindergartens are “kindies,” etc. Never heard brekkie but it’s a logical extension.

Howl April 5, 2013 at 4:50 pm

“Once I saw the number of calories in all that stuff, I lost my appetite for fast food.”

Once I saw the number of calories I could purchase for the two bucks I had, I loved fast food.

(Dept. of Unintended Consequences: posted calorie counts might have been mandated for the reason of wanting to “do something” about obesity, but I can’t be the only one who, in poorer moments, has used them to figure out how to get maximum caloric bang for my literal buck.)

Fhlhgiylglihglih April 5, 2013 at 12:17 am

I’m BMI slim due to my high stress, high amphetamine diet.

mw April 4, 2013 at 3:24 pm

I love the intellectual sophistication of this debate. Given McDonald’s, we find the presence of a supermarket doesn’t affect outcomes. From this, we’re told to conclude that supply interventions anywhere and everywhere in food don’t matter. Because it’s “clear” and “proven” that if there were a McDonald’s-equivalent of *somewhat* healthier food say, truly equally cheap, fast, and easy, it follows just by “simple” logic that people would never ever substitute it for actual McDonald’s.

MalthusianDelight April 4, 2013 at 4:02 pm

I’m not sure what you’re saying. Weren’t they covering that argument when they addressed the lack of purchasing the salads and a water rather than a Big Mac and Coke?

Hazel Meade April 4, 2013 at 4:40 pm

There already are places like “Chopped” the salad chain. Which is just as fast, cheap and healthy as McDonalds.

It’s just not as popular as McDonalds, because, surprisingly, salads don’t taste as good to the average human as hamburgers and fries.

It’s not that people eat at mcDonalds because it’s there and nothing else is. The McDonalds is there because people choose to eat at it. If there was a demand for healthy fast food, there would be a Chopped in place of the McDonalds.

Hazel Meade April 4, 2013 at 4:41 pm

Er, it’s as fast and cheap as a McDonalds, but is probably healthier.

Jan April 4, 2013 at 9:46 pm

Yeah, Chop’t is not as cheap as McDonald’s.

mw April 4, 2013 at 4:59 pm

That’s why I said *somewhat.* That just *makes* my argument–”salads” are one of the least appetizing, most thoughtless ways to serve vegetables that says as clearly as can be said “we don’t care.” South India, for example, is a place where most people live off of vegetables, beans, fruit, and nuts, yet you’d be hard-pressed to find them eating “salads.” The point is that it would take time and effort for McDonald’s to serve creative, hot, flavorful vegetable dishes. Serving salads is a way to pay lip service while ensuring that no one actually eats healthily. Ditto Chopt

Cliff April 4, 2013 at 6:08 pm

Salads are very popular in the United States. Are you proposing that successful salad chains should start selling foods that REALLY no one eats?

mw April 4, 2013 at 6:42 pm

I suppose I’m saying a few things: (1) the population amongst whom salads are ‘very popular’ is likely distinct from that which frequents McDonalds, (2) the type of vegetable dish most likely to appeal to the type who frequents McDonalds are likely most anything but salads (where salad means a bunch of raw vegetables mixed together), (3) the nutritional content of, say, a Qdoba or Chipotle burrito of the fried vegetables, beans, guacamole, brown rice etc variety is much closer to a salad than to a Big Mac.

revver April 4, 2013 at 7:23 pm

Bingo: A person who is health-conscious isn’t likely to darken the door of a mcdonalds for any reason, salad or not.

Hasdrubal April 5, 2013 at 9:35 am

“The point is that it would take time and effort for McDonald’s to serve creative, hot, flavorful vegetable dishes….”

Time + effort = expensive

McDonalds faces constraints because their customers go there for convenience and are price conscious. Another down side to vegetable dishes is that you can’t smother them in fat and salt to make them palatable, you need some fresh, decent ingredients. That seriously complicates the supply chain, further increasing expenses. Chipotle is more expensive than McDonalds for a reason.

mw April 5, 2013 at 12:31 pm

Yep, I guess my point is, how is that not (partly) a supply issue?

Travis Ormsby April 4, 2013 at 3:38 pm

Wake me up when the study is linked to an actual health outcome, not just BMI.

Jan April 4, 2013 at 9:49 pm

There are a lot of questionable surrogate markers out there for health outcomes, but BMI is not one of them.

Jacob AG April 4, 2013 at 9:52 pm

+1

Vinnie April 4, 2013 at 10:43 pm

Thank you. I was wondering when someone was going to mention this very obvious point and not just talk about McDonald’s menu items. The conclusion seems very limited, and I’m really surprised that both Tyler and the author extrapolate “does not cause a significant increase in BMI” to “not a dietary issue.”

Wonks Anonymous April 4, 2013 at 3:39 pm

When it comes to drug policy, I thought “demand side” policies involved arresting/stinging users, tainting legal/controlled substances to make abuse more lethal, putting users in drug treatment or some such. And libertarians would generally oppose those as well.

Jacob AG April 4, 2013 at 10:05 pm

Yes, libertarians would opposing arresting (most) drug users.

Poisoning drugs isn’t a demand-side policy, in fact I don’t think it’s even a policy.

And a libertarian would probably oppose *forcing* drug users into treatment, but would support offering treatment over arresting users, for sure.

Note that consistency among libertarians with respect to approaches to the supply side of food and approaches to the supply side of drugs, does not necessarily imply consistency with respect to supply and demand for drugs.

mike April 4, 2013 at 10:31 pm

“Poisoning drugs isn’t a demand-side policy, in fact I don’t think it’s even a policy.”

yeah, I lol’d at that too

Sam April 4, 2013 at 4:39 pm

For example, when you last ordered food at McDonald’s, did you even notice those ten salads on the menu? Did you order them? No, and me neither.

Might it not be the case that people have limited willpower. Once you’re standing in line at McDonalds and smelling the fries, it’s difficult to resist your favourite big mac, large fries and two bladderfuls of soda, but if you don’t go to McD at all, you might be happy at VeggiesRUs.

Hazel Meade April 4, 2013 at 4:44 pm

Watch out, you might be implying that fat people are fat because they are undisciplied and lack willpower. Which is verboten.

Mike Hess April 5, 2013 at 1:07 am

Perhaps the implication is that many people lack discipline and willpower, and therefore people inundated with tempting bad choices will have worse outcomes than people who face a higher proportion of less seductive, better choices.

Jody April 4, 2013 at 5:06 pm

I have a similar problem. Once I’ve already chewed the food, I find it difficult to not to swallow. But if I had put veggies in my mouth instead…

Ultimately, you choose to go to McDonald’s. You know what you’re going to order. Maybe not the first time or even the second, but well before you’ve gotten obese from gorging on Mickey D’s, you *should* know that you won’t be able to follow through on your salad plans and it’s still your own fault for deciding to go there.

Jacob AG April 4, 2013 at 9:57 pm

1) Yes, and note that limited willpower is a demand-side problem. If someone’s goal is to make money by selling food, and that demand-side problem exists, then they’ll take advantage of it (or someone will anyway). Hence you can’t just pay a bunch of supermarkets to go into food deserts hoping that access will beget healthy eating.

2) Where is there a VeggiesRUs? #SeriousQuestionFromAFatGuy

dearieme April 4, 2013 at 5:15 pm

It must have been more than 10 years ago that a paper in the BMJ demolished the rubbish about “food deserts”. The researchers basically just walked around an alleged “desert” or two, and noted all the good food for sale.

Jacob AG April 4, 2013 at 9:55 pm

Would love to see a link…

So Much For Subtlety April 5, 2013 at 12:18 am

Is it this one:

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1123946/?

That took me two seconds and a search engine so I would not swear to it.

anon April 5, 2013 at 9:03 am
JasonL April 4, 2013 at 5:16 pm

As someone upthread suggested, a big part of this is that groceries supply what consumers demand and fresh produce is first to spoil. You can’t ask a grocery to throw out tons of spoilage per week in the hopes that a few more people get arugula. In all of these places, there are frozen vegetables which are nutritionally quite good. Consumption isn’t high, but those aisles do exist in almost every store in every neighborhood.

Michael April 4, 2013 at 7:02 pm

I think in terms of supply side for drugs, there gets to be a ‘tipping point.’ Before the tipping point, supply side interventions are perhaps restricting the number of new users. I think in re: food, the analogous argument seems to me that there is a tipping point for healthy food. I heard of a black fellow who lived poor in a previous generation in a medium sized Texas town. He had heard of principles of healthy eating and thought it smart to drink V-8 juice and, in part for economic reasons, walked wherever he went. He lived into his 90′s.

Jacob AG April 4, 2013 at 10:10 pm

This is certainly possible. In the post I give the example of children as one example of people for whom supply-side interventions are perfectly appropriate, precisely because their demand curves are different from those of adults (i.e. they are non-existent). Everything a child consumes is an externality imposed by the parent. Given that the parent has no particular need to eat the same things as his/her child, there is no particular reason not to feed children healthy food (or keep them away from drugs, or guns, or you-name-it).

Anthony April 5, 2013 at 3:22 pm

Do you have children? Children definitely do have demand curves for food, and while younger children don’t have money to exercise their choices, they have other ways of making their demands known.

Jacob AG April 6, 2013 at 2:35 pm

Recall what a demand curve is. It is *not* how much of something you want to buy given a vector of prices. It is how much you are willing AND ABLE to of something to buy given a vector of prices. Kids are not able to buy anything, for the most part, especially at younger ages (as you get older, this becomes less and less true, but starting from birth this is the case).

So their demand curves are somewhere between meaningless and heavily watered down. Never mind high schoolers for a moment, they are a borderline case. Instead picture the elementary school student who eats 85% of his lunches at school. His demand curve basically doesn’t exist, and his diet is an externality. Point being, he has no demand curve, his whole quantity consumed of everything edible at school is an externality, so you might as well supply him with healthy foods rather than unhealthy ones. That is a policy that’s actually feasible, precisely because there is no demand curve. Adults *do* have demand curves, and they tend to be sort of inelastic when it comes to a) sugar-water and b) water, so adjusting their quantities consumed by fiddling with their supply curves of each is much more difficult than children.

revver April 4, 2013 at 7:26 pm

he he “Tipping point”, I see what did there.

Ricardo April 4, 2013 at 11:26 pm

You can get fat from eating salads (just drench them with high-fat salad dressing) and you can lose weight from eating twinkies and donuts or, as one commenter above pointed out, going on a scotch-and-KFC diet. There really isn’t any good reason to overturn conventional wisdom: you get fat from eating too many calories and you lose weight when you reduce your caloric intake.

All this is to say that obesity is just one aspect of health. Terrible eating habits will catch up to you eventually — it just might not be through weight gain if you are careful about how many calories you take in.

Jacob AG April 5, 2013 at 12:12 am

Put me down for the scotch-and-KFC diet.

Lou April 5, 2013 at 12:08 am

“Within a couple of miles of almost any urban neighborhood, “you can get basically any type of food,” said Roland Sturm of the RAND Corporation, lead author of one of the studies. “Maybe we should call it a food swamp rather than a desert,” he said.”
http://www.nytimes.com/2012/04/18/health/research/pairing-of-food-deserts-and-obesity-challenged-in-studies.html?_r=2&hp&

Anon April 5, 2013 at 1:50 am

I read this title as the “dessert” that comes after the meal… (eg. often cake or pie). Was very confused when I started reading the post. Didn’t realize how important that extra “s” was until now.

Not surprised at the result of the study though.

Vince April 5, 2013 at 5:29 am

One pound actually sounds fairly big to me, as the average effect. One pound is roughly equal to the increase in the average American’s weight over a 2 year period (given the rate over the past few decades), so having a supermarket essentially sets the clock back 2 years on the obesity epidemic. At current margins it translates into roughly a 1 percentage point drop in the percent of Americans who are obese (BMI 30+).

If obesity reduces life expectancy by 6 years on average (a number that Wikipedia gives), then that suggests that having a supermarket in the neighborhood increases a person’s life expectancy by about 3 weeks, on average. If the statistical value of a life-year is about $100,000, that suggests that having a supermarket in your neighborhood is worth over $5,000 on average, just for the health benefits.

mike April 5, 2013 at 10:00 am

And how did you turn “one pound” into “one pound per year” again?

David April 5, 2013 at 12:45 pm

“And how did you turn “one pound” into “one pound per year” again?”

He didn’t.

He’s using a hypothetical one-time drop of 1 pound across the entire US to approximate the benefit of a supermarket for one person.

losing 1 lb = going backwards 2 years on obesity epidemic = 1 percentage point drop in number of obese Americans over the last 2 years
1 percentage point decrease * 6 years shorter life expectancy for an obese individual = ~3 weeks of longer life per person
3 weeks * $100,000 statistical value of life-year = ~$5,000

The “over 2 years” part of the derivation is cancelled in line 1 where moving back 2 years (numerator) is negated by the pp change over the last 2 years (denominator).

David April 5, 2013 at 12:50 pm

That didn’t format correctly. Should be:

losing 1 lb = going backwards 2 years on obesity epidemic = 1 percentage point drop in number of obese Americans over the last 2 years

1 percentage point decrease * 6 years shorter life expectancy for an obese individual = ~3 weeks of longer life per person

3 weeks * $100,000 statistical value of life-year = ~$5,000

Vince April 5, 2013 at 3:42 pm

Over the past couple decades, the average weight in the US has been increasing by about half a pound each year. During the past couple of decades, the percentage of Americans who are obese has been increasing by about half a percentage point per year. So if a group of Americans change their weight by one pound, that suggests that (on average) we’d expect the percentage of them who are obese to change by about one percentage point.

Another way to put it: “What is the effect of adding one full-service supermarket to a neighborhood?” If the answer in the study is that on average, people who live within a mile of the supermarket have their BMI reduced by .115. My 20 minutes of googling & calculating suggest that the following answers are all roughly equivalent to that answer:

- On average, people who live within a mile of the supermarket lose 1 pound
- Within a mile of the supermarket, the obesity epidemic is set back 2 years
- There is a 1 percentage point drop in the obesity rate among people who live within a mile of the supermarket
- On average, people who live within a mile of the supermarket gain 3 weeks of life expectancy
- On average, people who live within a mile of the supermarket gain $5,000 worth of DALYs

Many of these numbers could easily be off by a factor of 2 in either direction, but they at least give order of magnitude estimates. Most of the uncertainty, I suspect, comes from the estimate of .115 in BMI in the original study.

Jacob AG April 6, 2013 at 2:27 pm

This is an important point — that 1 pound is significant — but it’s important to keep in mind that this study is really just looking at correlations. We really don’t know which way causality runs, which is the bigger issue.

I would also note (in support of Vince’s point about 1 pound being significant) that there might be a Flaw of Averages going on here. For all we know the effect is zero for 98% of people, but 2% of people are getting significantly fatter because they’re *not* driving far to get to a supermarket, or whatever. Point being it could be a small number of outliers driving the effect, which is “small” but hey, even 1 case of obesity can be a tragedy.

ThomasH April 5, 2013 at 6:29 am

Thanks for bringing Geller to your readers’ attention. I think he deserves more reads. From the number of comments, he does not seem to be getting many.

ykevivnege April 9, 2013 at 11:51 pm

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