Meat and Cancer

If you paid attention at all to the news yesterday, you surely saw the headlines proclaiming that bacon causes cancer.  The news came out of the ruling of a committee (the International Agency for Research on Cancer, IARC) for the World Health Organization.  (By the way, this is the same committee a couple months ago that made news when they announced glyphosate - aka Roundup - was carcinogenic). 

What follows is a pointer to two of best analyses of the announcement I saw followed by my own thoughts.  

Here's Ed Yong at the Atlantic.

“Here’s the thing: These classifications are based on strength of evidence not degree of risk.

Two risk factors could be slotted in the same category if one tripled the risk of cancer and the other increased it by a small fraction. They could also be classified similarly even if one causes many more types of cancers than the other, if it affects a greater swath of the population, and if it actually causes more cancers.

So these classifications are not meant to convey how dangerous something is, just how certain we are that something is dangerous.

But they’re presented with language that completely obfuscates that distinction.”

Then, in what is sure to become a classic line, Yong wrote:

“Perhaps we need a separate classification scheme for scientific organizations that are “confusogenic to humans.””

Over at Grist, Nathanael Johnson wrote the following

“What if you just want a sausage once every other week or so? The thing to keep in mind here is that IARC’s job is to figure out if substances can cause cancer, not if they’re likely to. It’s findings aren’t that useful to normal people looking for advice on how to live their lives.”

So, we need to keep in mind that the old adage that the dose makes the poison.  And, we need to look at relative risks.  Such as this one offered by Johnson:

“If today you start eating 50 grams a day (about three strips of bacon) more processed meat than usual, your risk of cancer increases 18 percent. For comparison, if you are a nonsmoker who starts smoking three cigarettes a day, your risk of lung cancer increases 600 percent.”

One thing rarely communicated in these sorts of reports is the baseline level of risk.  Let's use Johnson's example and suppose that eating three pieces of bacon everyday causes cancer risk to increases 18%.  From what baseline?  To illustrate, let's say the baseline risk of dying from colon cancer (which processed meat is supposed to cause) is 2% so that 2 out of every 100 die from colon cancer over their lifetime (this reference suggests that's roughly the baseline lifetime risk for everyone including those who eat bacon).  An 18% increase means your risk is now 2.36% for a 0.36 percentage point increase in risk.  I suspect a lot of people that would accept a less-than-half-a-percentage point increase in risk for the pleasure of eating bacon.

Now, let's suppose instead that the baseline risk was 10% (10 out of 100 die from cancer).  In this case, an 18% increase means your risk of cancer is now 11.8% for a 1.8 percentage point increase in chance of dying of colon cancer.  Thus, the same percentage increase in risk (18%) results in very different changes in absolute likelihoods of dying (an increase of either 0.36 percentage points or 1.18 percentage points) depending on the baseline starting point.  In a population of 1000 people who started eating 3 pieces of bacon, in one case we'd have about 3.6 extra people die and 11.8 extra people die in the other.  That's more than three times as many people dying in the high-baseline risk case than in the low-baseline risk case. In short, studies that say that eating X causes a Y% increase in cancer are unhelpful unless I know something about my underlying, baseline probably of cancer is without eating X.

Is the growth in agricultural productivity slowing?

Last week I gave a talk at the University of Nebraska, and Julian Alston from UC Davis was also there.  He presented some recent research with Matt Anderson and Phil Pardey about productivity growth in agriculture.  While I have seen some discussions about the possibility of a slowdown in productivity growth in developing countries, Alston's research suggest it is a phenomenon alive and well here at home.  This is important stuff.  Falling productivity growth has important implications for sustainability, food security, and research and development. They write: 

“We detect sizable and significant slowdowns in the rate of productivity growth. Across the 48 contiguous states for which we have very detailed data for 1949– 2007, U.S. multifactor productivity (MFP) growth averaged just 1.18 percent per year during 1990–2007 compared with 2.02 percent per year for the period 1949–1990. MFP in 44 of the 48 states has been growing at a statistically slower rate since 1990. Using a longer-run national series, since 1990 productivity growth has slowed compared with its longer-run growth rate, which averaged 1.52 percent per year for the entire period, 1910–2007. More subtly, the historically rapid rates of MFP growth during the 1960s, 1970s and 1980s can be seen as an aberration relative to the long-run trend. A cubic time-trend model fits the data very well, with an inflection around 1962. We speculate that a wave of technological progress through the middle of the twentieth century—reflecting the progressive adoption of various mechanical innovations, improved crop varieties, synthetic fertilizers and other chemicals, each in a decades long process—contributed to a sustained surge of faster-than-normal productivity growth throughout the third quarter of the century. A particular feature of this process was to move people off farms, a one-time transformation of agriculture that was largely completed by 1980.”

Here's a graph from their paper showing the change in proportional growth rate in yields (i.e., the log of yields) over time for 6 crops with the inflection point indicated for when growth rates began decelerating.  

Krugman on Food Policy

As incoming president of the Agricultural and Applied Economics Association, I would have loved to have seen one of our food or agricultural economist members featured at the New York Time's Food for Tomorrow conference that focused on food policy earlier this week.  That didn't happen, but at least they did have a prominent general economist on  program.  Paul Krugman's remarks are below.

He talked a bit about externalities.  I wrote on that topic in this paper.  I also brought it up when recently discussing nutritional guidelines: 

“But, what about externalities? To the extent beef production uses a lot of corn or land, that’s already reflected in the price of beef. But, does the price of beef reflect water use and potential (long run) impacts of greenhouse has emissions? Probably not fully. So, the key there is to try to get the prices right. Well functioning water markets would be a start. Greg Mankiw recently had an interview on getting the price of carbon right. Once the prices are right, then “recommendations” regarding resource use are somewhat meaningless: you’re either willing to pay (and able) the price to buy the items you like to eat or not. ”

He argues that if the externalities were properly priced organic would be no more expensive and "industrial" food would be more expensive.  I'm not so sure about that and he doesn't cite any actual evidence to support the claim.  But, here's the thing.  Let's say we had a carbon tax or carbon market.  Now we wouldn't need to answer that question or cajole people about eating organic or non-organic.  I think that was basically his answer to the 1st question that was asked.  

I was also happy to hear him say at some point, "I'm not an expert on any of this" because at a few points he seemed a bit out of his depth on the subject matter and was pandering to the audience.  That being said, I'm at least happy a good economist was in the room contributing to the debate.  His answer to the last question (at about the 22 minute mark) was pretty much right on target.

Potential Impacts of GMO Cowpeas in Africa

The journal Agricultural Economics recently published a paper I co-authored with Sika Gbègbèlègbè who now works for the International Livestock Research Institute (other coauthors are Jess Lowenberg-DeBoer, Razack Adeoti, and Ousmane Coulibaly).  

The abstract:

“Genetically modified (GM) crops could increase economic growth and enhance living standards in Africa, but political issues have slowed the use of biotechnology. This is the first study that assesses the potential impact of GM crops in Africa while considering the preferences of producers and consumers towards GMOs as well as the income and price risks they face. The study uses a choice experiment to estimate the ex ante economic impact of a novel technology, Bacillus thuringiensis (Bt) cowpea, on producers and consumers in Benin, Niger and northern Nigeria. The experiment involves the simulation of a market transaction similar to those in open air markets in West Africa. During the market simulation, respondents are informed about the advantages and disadvantages, including health risks, of Bt cowpea. The results from the study suggest that cowpea growers and consumers in Benin and northern Nigeria prefer Bt to conventional cowpea for health safety reasons. The results estimate that social welfare in Benin, Niger and northern Nigeria would increase by at least US$11.82 per capita annually with Bt cowpea, if seed sectors are operating smoothly. With inefficiencies in seed sectors and the potential for cowpea acreage increase, the estimated social welfare increase in the region would be about US$1.26 per capita annually.”

Assorted Links

How dangerous is obesity, high blood pressure, and high cholesterol?  This post helps put our fears in perspective.  A quote:

“if you’re 35 and not a smoker, you have a 98.5% chance of making it to 45. At 45, you would re-calibrate with those that are still alive and there is a 96% chance of living ten more years, then 93% for the next ten, then 90% for the next. Finally, at age 75, life gets a little risky and the chance that you will live another ten years drops to only 65%. Essentially, the ten year risk of death is almost negligible until we get to our 70s.”

File in the folder "Unintended Consequences".  Researchers find that a ban on bottled water on the University of Vermont campus (presumably to cut down on waste) led to more plastic bottles being shipped to campus and to more soda consumption.

Ways to promote animal welfare without being a vegetarian.  (though not explicitly acknowledged, some of the thoughts flow from my book with Bailey Norwood, Compassion by the Pound)

A great summary article by Phil Pardey and colleagues in the American Journal of Agricultural Economics on funding for research and development in agriculture.  They write:

“We reveal that the U.S. position in the global R&D landscape has changed in substantive ways, especially over the past decade, partly as a result of investment decisions taken by governments and private entities elsewhere in the world, but also as a consequence of changed investment priorities in the United States”

Later they write:

“While the United States is arguably still the predominant source of innovation in global agriculture, the tide appears to be turning”

What happens when Big Food buys Little Food?  File under: organic isn't little anymore . . .