Slow down there

Max Fisher has a piece in the Washington Post presenting "The amazing, surprising, Africa-driven demographic future of the Earth, in 9 charts". While he notes that the numbers are "just projections and could change significantly under unforeseen circumstances" the graphs don't give any sense of the huge uncertainty involved in projecting trends out 90 years in the future. Here's the first graph:

 

The population growth in Africa here is a result of much higher fertility rates, and a projected slower decline in those rates.

But those projected rates have huge margins of error. Here's the total fertility rate, or "the average number of children that would be born to a woman over her lifetime"  for Nigeria, with confidence intervals that give you a sense of just how little we know about the future:

That's a lot of uncertainty! (Image from here, which I found thanks to a commenter on the WaPo piece.)

It's also worth noting that if you had made similar projections 87 years ago, in 1926, it would have been hard to anticipate World War II, hormonal birth control, and AIDS, amongst other things.

Typhoid counterfactuals

An acquaintance (who doesn't work in public health) recently got typhoid while traveling. She noted that she had had the typhoid vaccine less than a year ago but got sick anyway. Surprisingly to me, even though she knew "the vaccine was only about 50% effective" she now felt that it was  a mistake to have gotten the vaccine. Why? "If you're going to get the vaccine and still get typhoid, what's the point?" I disagreed but am afraid my defense wasn't particularly eloquent in the moment: I tried to say that, well, if it's 50% effective and you and, I both got the vaccine, then only one of us would get typhoid instead of both of us. That's better, right? You just drew the short straw. Or, if you would have otherwise gotten typhoid twice, now you'll only get it once!

These answers weren't reassuring in part because thinking counterfactually -- what I was trying to do -- isn't always easy. Epidemiologists do this because they're typically told ad nauseum to approach causal questions by first thinking "how could I observe the counterfactual?" At one point after finishing my epidemiology coursework I started writing a post called "The Top 10 Things You'll Learn in Public Health Grad School" and three or four of the ten were going to be "think counterfactually!"

A particularly artificial and clean way of observing this difference -- between what happened and what could have otherwise happened -- is to randomly assign people to two groups (say, vaccine and placebo). If the groups are big enough to average out any differences between them, then the differences in sickness you observe are due to the vaccine. It's more complicated in practice, but that's where we get numbers like the efficacy of the typhoid vaccine -- which is actually a bit higher than 50%.

You can probably see where this is going: while the randomized trial gives you the average effect, for any given individual in the trial they might or might not get sick. Then, because any individual is assigned only to the treatment or control, it's hard to pin their outcome (sick vs. not sick) on that alone. It's often impossible to get an exhaustive picture of individual risk factors and exposures so as to explain exactly which individuals will get sick or not in advance. All you get is an average, and while the average effect is really, really important, it's not everything.

This is related somewhat to Andrew Gelman's recent distinction between forward and reverse causal questions, which he defines as follows:

1. Forward causal inference. What might happen if we do X? What are the effects of smoking on health, the effects of schooling on knowledge, the effect of campaigns on election outcomes, and so forth?

2. Reverse causal inference. What causes Y? Why do more attractive people earn more money? Why do many poor people vote for Republicans and rich people vote for Democrats? Why did the economy collapse?

The randomized trial tries to give us an estimate of the forward causal question. But for someone who already got sick, the reverse causal question is primary, and the answer that "you were 50% less likely to have gotten sick" is hard to internalize. As Gelman says:

But reverse causal questions are important too. They’re a natural way to think (consider the importance of the word “Why”) and are arguably more important than forward questions. In many ways, it is the reverse causal questions that lead to the experiments and observational studies that we use to answer the forward questions.

The moral of the story -- other than not sharing your disease history with a causal inference buff -- is that reconciling the quantitative, average answers we get from the forward questions with the individual experience won't always be intuitive.

African population density

I was recently struck by differences in population density: Northern Nigeria's Kano state has an official population of ~10 million, whereas the entire country of Zambia has 13.5. Zambia's land area, meanwhile, is also about 35 times that of Kano. So I started looking around for a nice map of population density in Africa. The best I found was this one via UNEP:

And here's a higher resolution version.

Some of the most striking concentrations are along the Mediterranean coast, the Nile basin, the Ethiopian plateau, and around Lake Victoria. (I'd love to track down the data behind this map but haven't had time.)

A good map can change how you think. If you're used to seeing maps that have country-level estimates of disease prevalence, for instance, you miss variations at the subnational level. This is often for good reason, as the subnational data is often even spottier than the national estimates. But another thing you miss is a sense of absolute population numbers, because looking at a map it's much easier to see countries by their areas rather than their populations, which for matters of health and other measures of human well-being is generally what we care about. There are some cool maps that do this but they inevitably lose their geographic accuracy.

Transatlantic

Gumbo, a favorite food in the southern United States, particularly in the Louisiana area, is a variation of popular west African (including Yoruba) stews in which similar ingredients, such as okra and spicy peppers, are served over a starchy substance. In west African stews the starch is usually yam or cassava; in gumbo it is usually rice. West African language patterns have also merged with the English language over time. For example, the Yoruba language does not conjugate verbs. Therefore, the English “I am,” you are,” he/she/it is,” translates into Yoruba simply as “emi ni,” iwo ni,” and “oun ni” respectively. Scholars equate this lack of conjugation with colloquial African-American speech patterns that would conjugate the same phrase in English as “I be,” “you be,” he/she/it be,” representing the retention of African language patterns over time and space….

From A History of Nigeria by Falola and Heaton.

Monday miscellany

A day late, but "Tuesday miscellany" loses the alliteration:

  • "Promoting professional networks at work", by Ian Thorpe, who writes the blog "Knowledge Management on a Dollar a Day". This post has a lot of practical advice for organizations, especially when onboarding new staff.
  • "Does it take a village?" by Paul Starobin in Foreign Policy, examines Jeff Sachs, the Millennium Villages Project, and their evaluation plans. For those who have been following the subject for a while there's some interesting background material worked into the piece that I hadn't read before.
  • "On what do health economists agree?" asks the Incidental Economist. The penultimate point (on inequality) is the only one I thought didn't seem widely agreed, and the blog comments concur.
  • Causal inference: extrapolating from sample to population, via the Monkey Cage. This paper argues that findings done with multiple regression from supposedly representative samples aren't necessarily representative; seems likely to become widely read and discussed.
  • Berk Ozler of the World Bank Development Impact blog shares some enlightening comparisons of medical and economic journals.
  • Finally, Hans Rosling explains population growth and climate change (with Legos!).

On economic history

Here’s an excerpt from Peter Temin’s “The Rise and Fall of Economic History at MIT.” (PDF, via Mankiw)

What is the cost of not having economic history at MIT? It can be seen in Acemoglu and Robinson, Why Nations Fail (2012). This is a deservedly successful popular book, making a simple and strong point that the authors made originally at the professional level over a decade before (Acemoglu, Johnson and Robinson, 2001). They assert that countries can be “ruled by a narrow elite that have [sic] organized society for their own benefit at the expense of the vast mass of people” or can have “a revolution that transformed the politics and thus the economics of the nation … to expand their economic opportunities (Acemoglu and Robinson, 2012, pp. 3-4).”

The book is not however good economic history. It is an example of Whig history in which good policies make for progress and bad policies preclude it. Only transitions from bad to good are considered in this colorful but still monotonic story. The clear implication is that if countries can copy the policies of English-speaking countries, they will prosper. No consideration is given to Britain’s economic problems over the past half-century or of Australia’s relative decline for a century.

His take on the US is also rather provocative – worth a read.

This seems like a good time to recommend Evolving Economics, a history of economics that I found helpful for supplementing my crash-course introduction to the field. It’s quite dense (I still haven’t been able to read it straight through) but was a good resource for looking up particular scholars, and for understanding the path-dependency and personalities behind the development of economics.

Americanah

Americanah, the new novel by Chimamanda Ngozi Adichie is very good. I have a long list of Nigerian fiction on my to-read list, but Americanah got bumped to the top because it seemed like the perfect transition from Princeton to Nigeria: I heard Chimamanda speak in Princeton – where she, like Ifemelu, the main character, lived for a year on a fellowship – a month or so ago. Americanah starts with Ifemelu taking NJ Transit from Princeton to Trenton to get her hair braided, because Princeton is the sort of place with an “ice cream shop that had fifty different flavors including red pepper” but no one to braid black hair. Following her TED Talk advice, Americanah crams in many narratives. It’s set in Lagos and London, Brooklyn and Baltimore, New Haven and Philly, and it’s about migration from Lagos to America, from Lagos to London, and from everywhere back to Nigeria. One character, in London:

His eyes would follow them, with a lost longing, and he would think: You can work, you are legal, you are visible, and you don’t even know how fortunate you are.

It’s about dating across race, wealth, and cultures; academics and intellectuals and the many people who are only one or the other, not both; the London black market of arranged sham marriages and faked ID documents; accents real and faked; sex work; the constant burdens and exploitation and desperation of the undocumented; Barack Obama; the hope and opportunity that can come with an approved visa application; and hair. Lots of hair.

There are Americans who deny that racism is still a problem. Wealthy folks who, learning Ifemelu is from Nigeria, try to connect by mentioning their latest trip to Tanzania, their opinion of Ethiopian beauty, the charity they support in Malawi. Ifemelu thinks:

There was a certain luxury to charity that she could not identify with and did not have…. Ifemelu wanted, suddenly and desperately, to be from the country of people who gave and not those who received, to be one of those who had and could therefore bask in the grace of having given, to be among those who could afford copious pithy and empathy.

Another character is at a London dinner party, thinking:

Alexa, and the other guests, and perhaps even Georgina, all understood the fleeing from war, form the kind of poverty that crushed human souls, but they would not understand the need to escape form the oppressive lethargy of choicelessness. They would not understand why people like him, who were raised well fed and watered but mired in dissatisfaction, conditioned from birth to look towards somewhere else, eternally convinced that real lives happened in that somewhere else, were now resolved to do dangerous things, illegal things, so as to leave, none of them starving, or raped, or from burned villages, but merely hungry for choice and certainty.

Ifemelu is, for a while, a blogger who writes “Raceteenth or Various Observations About American Blacks (Those Formerly Known as Negroes) by a Non-American Black” which gives Adichie a venue to make observations, often hilarious and/or impolite. One post starts:

Dear Non-American Black, when you make the choice to come to America, you become black. Stop arguing. Stop saying I’m Jamaican or I’m Ghanaian. America doesn’t care. So what if you weren’t “black” in your country? You’re in America now….

Americanah never dwells on a single theme until it becomes tiresome The major characters are sympathetic but flawed, and the observations are constantly insightful – I wanted to quote much more here. So, highly recommended.

Comparisons

It’s hard for me to experience Nigeria without comparing it – mentally, and probably too often, verbally, with Ethiopia. Or rather, comparing Abuja to Addis, since my experience in each country has been centered on the capital. A few thoughts with a broad brush stroke: compared to Addis, Abuja is hotter (lower altitude), the roads are much better (oil wealth? planned city?), the taxis and most cars are newer (less massive import taxes?), the driving is much more aggressive (cars that can actually go fast + fast roads), the upscale grocery stores have amazing selection (more Nigerian buying power?), and security and crime are much greater, ever-present concerns. The music is better (sorry, Teddy Afro) and the conversation louder. The international scene here is more British, more male, and – especially outside of Abuja – more ensconced in all-encompassing compounds called “life camps” run by big foreign oil and construction companies that, like NGOs, often have 3-letter acronym names that have long outlived their original meaning.

Monday miscellany: on my reading list

NYC and London from the air

My recent New York to London flight featured both good approach paths and nice weather, so I snapped a few shots. Here's New York, taking off:

And London:

I was going to include a quote here from Gotham, an epic and impressively readable history of New York City, regarding how communication and travel times between London and New York decreased during the 17th and 18th centuries, but can't find the quote readily now... So, short version: things got faster.

Next up!

After three years, I'm done with grad school! I finished my MSPH (Global Disease Epidemiology and Control focus) at Hopkins in late May, and my MPA (Economics and Public Policy focus) at Princeton in early June. It's been a lot of work: 10 months of internships, 3 comprehensive qualifying exams, and a Masters thesis; plus 4 quarters of Hopkins classwork and 3 semesters of Princeton classwork for a total of 33 graduate classes. I loved being in school again -- not all my classmates did -- but I'm also happy to have wrapped things up. One consequence of studying applied subjects like public health and public policy is that you're rarely delving into a subject just for kicks (at least for long); the goal is always to get out and do good work with the knowledge and skills you've acquired. This week I started a job I'm really excited about: working with the Clinton Health Access Initiative (CHAI)'s Applied Analytics Team. If you're curious about CHAI here's their about page, and this profile of Elizabeth McCarthy tells a bit more about the Applied Analytics Team (which she runs). We're also hiring. As with my previous internships and work, I won't be writing directly about what I'm doing much at all, but I'll still be writing more broadly about global health and development policy. (And this is probably a good time to reiterate that the views here are just my own.) I'll be working on projects throughout sub-Saharan Africa -- I'm headed to Nigeria for a couple months on Saturday! More on that soon.

Now, back to my (ir)regular blogging...

Several job opps

Some other good places to look for jobs: mHealth student Google group and the African Development Jobs blog.

"What is wrong (and right) in economics?"

Economist Dani Rodrik has a great essay up on his website on what's good and bad about economics. Here's a bit on the relationship between trade policy and growth:

I remember well the reception I got when I presented my paper (with Francisco Rodriguez) on the empirics of trade policy and growth. The literature had filled up with extravagant claims about the effect of trade liberalization on economic growth. What we showed in our paper is that the research to date could not support those claims. Neither the theoretical nor empirical literature indicated there is a robust, predictable, and quantitatively large effect of trade liberalization on growth. We were simply stating what any well-trained economist should have known. Nevertheless, the paper was highly controversial. One of my Harvard colleagues asked me in the Q&A session: “why are you doing this?” It was a stunning question. It was as if knowledge of a certain kind was dangerous.

There's a lot of good material in there about what economics is and isn't, and how to do it better.  I had forgotten that Rodrik studied at Princeton, so was pleasantly surprised by this:

However, contemporary economics in North America has one great weakness, and that is the excessive focus on methods at the expense of breadth in terms of social and historical perspective. PhD programs now train applied mathematicians and statisticians rather than real economists. To become a true economist, you need to do all sorts of reading – from history, sociology, and political science among other disciplines – that you are never required to do as a graduate student. The best economists today find a way of filling this gap in their education. I consider myself very lucky that I was a political science major and did a master’s in public affairs (as it is called at Princeton) before I turned to economics. I say lucky, because some of my best work – by my judgement, at least – was stimulated by questions or arguments I encountered outside of neoclassical economics.

"When public health works, it's invisible"

Caitlin Rivers' post on the "public health paradox: why people don't get flu shots" hits the nail on the head:

Unfortunately, the root of this problem is deep. The problem is that when public health works, it is invisible. It's an insidious, persistent public relations issue that plagues public health. Nobody sees when a chain of disease transmission is broken, or when contaminated food is prevented from reaching the market, or when toxic pollutants don't enter the environment. That's the point: the goal of public health is prevention, not reaction....

What then can be done to counteract these misperceptions? First, public health needs to be more vocal about its successes. This graphic of crude death rates for infectious diseases during the 19th century, for example, should be widely disseminated. A little self-promotion could go a long ways.

That's one reason I like Millions Saved, from the Center for Global Development -- it highlights "proven success in global health." One of the things that struck me when reading it was that most of the people who benefited from these interventions and programs would have no way of knowing that they benefited.

For another positive take, check out Charles Kenny's book Getting Better.

 

Monday miscellany

(Not) knowing it all along

David McKenzie is one of the guys behind the World Bank's excellent and incredibly wonky Development Impact blog. He came to Princeton to present on a new paper with Gustavo Henrique de Andrade and Miriam Bruhn, "A Helping Hand or the Long Arm of the Law? Experimental evidence on what governments can do to formalize firms" (PDF). The subject matter -- trying to get small, informal companies to register with the government -- is outside my area of expertise. But I thought there were a couple methodologically interesting bits: First, there's an interesting ethical dimension, as one of their several interventions tested was increasing the likelihood that a firm would be visited by a government inspector (i.e., that the law would be enforced). From page 10:

In particular, if a firm owner were interviewed about their formality status, it may not be considered ethical to then use this information to potentially assign an inspector to visit them. Even if it were considered ethical (since the government has a right to ask firm owners about their formality status, and also a right to conduct inspections), we were still concerned that individuals who were interviewed in a baseline survey and then received an inspection may be unwilling to respond to a follow-up. Therefore a listing stage was done which did not involve talking to the firm owner.

In other words, all their baseline data was collected without actually talking to the firms they were studying -- check out the paper for more on how they did that.

Second, they did something that could (and maybe should) be incorporated into many evaluations with relative ease. Because findings often seem obvious after we hear them, McKenzie et al. asked the government staff whose program they were evaluating to estimate what the impact would be before the results were in. Here's that section (emphasis added):

A standard question with impact evaluations is whether they deliver new knowledge or merely formally confirm the beliefs that policymakers already have (Groh et al, 2012). In order to measure whether the results differ from what was anticipated, in January 2012 (before any results were known) we elicited the expectations of the Descomplicar [government policy] team as to what they thought the impacts of the different treatments would be. Their team expected that 4 percent of the control group would register for SIMPLES [the formalization program] between the baseline and follow-up surveys. We see from Table 7 that this is an overestimate...

They then expected the communication only group to double this rate, so that 8 percent would register, that the free cost treatment would lead to 15 percent registering, and that the inspector treatment would lead to 25 percent registering.... The zero or negative impacts of the communication and free cost treatments therefore are a surprise. The overall impact of the inspector treatment is much lower than expected, but is in line with the IV estimates, suggesting the Descomplicar team have a reasonable sense of what to expect when an inspection actually occurs, but may have overestimated the amount of new inspections that would take place. Their expectation of a lack of impact for the indirect inspector treatment was also accurate.

This establishes exactly what in the results was a surprise and what wasn't. It might also make sense for researchers to ask both the policymakers they're working with and some group of researchers who study the same subject to give such responses; it would certainly help make a case for the value of (some) studies.

An uphill battle

I took this photo in the NYC subway a few days ago. My apologies for the quality, but I thought it's a great juxtaposition:

In the top of the photo is an ad from the NYC Department of Health, advising you to choose food with less sodium. (Here's an AP story about the ads.) But to the bottom right is an ad for McDonald's dollar menu, and those are everywhere. While it doesn't mean we shouldn't run such ads, it's worth remembering that the sheer volume of food advertising will always dwarf opposing health messages. 

Fun projects are fun

Jay Ulfelder, of the blog Dart-Throwing Chimp, recently wrote a short piece in praise of fun projects. He links to my Hunger Games survival analysis, and Alex Hanna's recent application of survival analysis to a reality TV show, RuPaul's Drag Race. (That single Hunger Games post has accounted for about one-third of the ~100k page views this blog got in the last year!) Jay's post reminded me that I never shared links to Alex's survival analysis, which is a shame, so here goes: First, there's "Lipsyncing for your life: a survival analysis of RuPaul's Drag Race":

I don’t know if this occurs with other reality shows (this is the first I’ve been taken with), but there is some element of prediction involved in knowing who will come out as the winner. A drag queen we spoke with at Plan B suggested that the length of time each queen appears in the season preview is an indicator, while Homoviper’s “index” is largely based on a more qualitative, hermeneutic analysis. I figured, hey, we could probably build a statistical model to know which factors are the most determinative in winning the competition.

And then come two follow-ups, where Alex digs into predictions for the next episode of the current season, and again for the one after that. That last post is a great little lesson on the importance of the proportional hazards assumption.

I strongly agree with this bit from Jay's post about the value of these projects:

Based on personal experience, I’m a big believer in learning by doing. Concepts don’t stick in my brain when I only read about them; I’ve got to see the concepts in action and attach them to familiar contexts and examples to really see what’s going on.

Right on. And in addition to being useful, these projects are, well, fun!

Rearranging the malarial deck chairs?

A friend sent this link to me, highlighting a critical comment about the future of the World Health Organization, in the context of the World Malaria Report 2012. Here's an excerpt of the comment by William Jobin:

Their 2012 Annual Report is a very disturbing report from WHO, for at least two reasons:

1. Their program is gradually falling apart, and they offer no way to refocus, no strategy for dealing with the loss in funding, nor the brick wall of drug and biocide resistance which is just down the road. There is a label for people who keep doing the same thing, but expect different results. Do you remember what it is?

2. Because the entire top management of WHO consists of physicians, they have no idea of the opportunities they are missing for additional funding and for additional methods to add to their chemically-oriented strategy...

Concluding with:

I am not sure WHO has much of a future, nor does the UN system itself, after their failure to prevent the wars in Libya and Syria. But as long as the UN and WHO continue to operate, they must refocus their approach to face the reality of a rapidly declining budget from UN sources. Instead, I see them just re-arranging the deck chairs on the Titanic.

My friend said, "I wish these comments (and issues with the WHO and UN) were more publicised! This is not the first time I am hearing of such issues with the WHO and its demise." I've certainly heard similar sentiments about the WHO from classmates and professors, but it seems there's much less open discussion than you might expect. I'd welcome discussion in the comments...