Book review: Plagues and the Paradox of Progress

When we went into lockdown earlier this year, I quickly gathered together some books from my office, not knowing how long it would be before I could return. One of those books was Plagues and the Paradox of Progress by Thomas Bollyky. It seemed quite relevant (perhaps too relevant) at the time, but I've only just gotten finished with reading it now.

The premise of the book is relatively simple. High-income countries took a long time to tackle their own problems of infectious disease (like cholera, typhoid, etc.), and in the process of tackling infectious diseases, those countries developed the types of institutions (like health systems) that have contributed to high income countries' ongoing success. In contrast, modern-day low-income countries haven't had to go through the same long process of institution building in order to combat infectious diseases, as they have been able to import the solutions from high income countries, often with the support of international aid or philanthropic donors. So, while infectious disease no longer kills millions of people in low income countries, the lack of effective institutions keeps those countries poor - that is what Bollyky terms the paradox of progress. As Bollyky summarises:

...the world has gotten better in ways that should make us worry. The last two decades have brought dramatic reductions in endemic infectious disease and child mortality, but not the improvements in health-care systems, responsive governance, and employment opportunities that accompanied these changes in wealthier nations in the past. 

On the face of it, it's a compelling narrative, supported by what is among the most extensively researched evidence base I've seen in a book (for instance, Chapter 4 is 34 pages, but has 180 endnotes of references). However, the narrative is not entirely convincing, because it lacks strong causal evidence. It is all very well to present lots of evidence of how bad infectious diseases were in the past, and describe how high income countries dealt with them, but quite another to export that experience to low income countries. If you're not able to first establish the causal links, then your evidence base is at best partial. This is one of the problems that the Kuznets Curve faces - it looks good based on the experience of high income countries, but falls apart when exposed to data from low income countries.

I feel like the book also dramatically oversimplifies the issues. The role of institutions in economic development involves a huge literature, on which Bollyky barely touches the surface. To some extent, that's because that literature would broaden the scope of the book to an unmanageable extent. However, it also leaves the book without a clear relationship to a pretty important section of the literature.

It also leads to a policy prescription in the concluding chapter that can best be described as banal. I think almost anyone could have recommended secure property rights over land, and increased investment in education and primary health care, as important policy goals for low income countries, regardless of any link to infectious disease. And the links between those recommendations that the evidence in the preceding chapters is pretty tenuous, especially in the case of property rights.

Aside from those major gripes, the book is wonderfully well written and easy to read. And as I said, it is incredibly well sourced, so an interested reader can easily follow up on any of the evidence that Bollyky presents. The book also had some prescient moments that call to mind the current pandemic crisis:

Several years after the Ebola outbreak, coordination and funding of international epidemic and pandemic preparedness and response remain ad hoc and dependent on media attention. "We still are not ready for the big one," said Ron Klain, the former US Ebola czar, to the Washington Post in October 2017.

Indeed. Also this:

The United States was (and remains) woefully ill-prepared for the threat of antibiotic resistance and future pandemics.

As Americans have been discovering this year, to the dismay of many. However, Bollyky does make some clear errors, one of which is among my pet peeves - comparing stocks with flows:

The market capitalization of Philip Morris International at $187 billion (as of July 2017) is larger in nominal terms than the economies of most of the 180 countries where that company sells Marlboro and its other brands of cigarettes.

It may be technically true, but it's a worthless comparison, because a market capitalisation is a stock (based on fundamentals, it would be the present value of all future cash flows of the corporation), while GDP is an annual flow.

Overall, while the book was an enjoyable read, I don't feel like I learned much from it, and it certainly falls short of providing a convincing argument to me.

Professor gender and the gender gap in STEM

I've written a number of posts on the gender gap in economics, but also in STEM (science, technology, engineering, and maths) (see here for example). In some of those posts on economics, the research I've been discussing has highlighted the potential effect of role models on the gender gap.

If role models matter, then you'd expect the gender of professors to matter. The problem with evaluating that empirically is that students often have some choice over who their professors are, particularly in large classes early in their studies, where there may be many sections to choose from, or the same papers may be taught in multiple semesters. This 2010 article by Scott Carrell, Marianne Page (both University of California at Davis), and James West (US Air Force Academy), published in the Quarterly Journal of Economics (ungated earlier version here), is able to overcome that problem.

Carrell et al. use data from the US Air Force Academy, where:

...students are randomly assigned to professors for a wide variety of mandatory standardized courses.

That means that there will be no problems of selection bias, where students choose their own professors. In addition:

...course grades are not determined by an individual student’s professor. Instead, all faculty members teaching the same course use an identical syllabus and give the same exams during a common testing period.

That means that there is also no bias arising from differential grading between different professors. Carrell et al. have data from 9015 students from the USAFA graduating classes of 2001 through 2008. They focus their attention on mathematics, physics, chemistry, engineering, history, and English classes, and look at how the gender of the professor in each introductory class affects students' grades, the likelihood of taking further classes in the discipline, and the likelihood of graduating with a STEM degree. They find that:

...professor gender has only a limited impact on male students, it has a powerful effect on female students’ performance in math and science classes, their likelihood of taking future math and science courses, and their likelihood of graduating with a STEM degree. The estimates are robust to the inclusion of controls for students’ initial ability, and they are substantially largest for students with high SAT math scores.

Specifically, for female students:

...having a female professor reduces the gender gap in course grades by approximately two-thirds.

That is quite substantial, given that after controlling for mathematical ability, female students on average perform 15 percent of a standard deviation worse than male students, in STEM courses. However, it is notable that they also find that:

...at the top of the distribution... having a female professor completely closes the gender gap...

The effect on taking additional STEM classes and graduating with a STEM degree is also concentrated amongst female students with greater mathematical ability, and eliminates the gender gap in those measures as well.

However, the same effect of professor gender are not apparent in the humanities:

 In contrast, the gender of professors teaching humanities courses has, at best, a limited impact on students’ outcomes.

 All of this suggests that, if we want to narrow the gender gap in STEM, particularly amongst the most able female students, universities would need to employ more female teaching staff. However, Carrell et al. bury a very important caveat in a footnote on the last page of their article:

Note that the impact of female professors may reflect the high quality of faculty at the USAFA, and that substituting lower-quality female professors for high-quality male professors is not a policy that would be recommended by the authors.

Universities need to fully understand the trade-offs before they jump into a policy response. And also, USAFA is a pretty unique environment, so it would be good to know if similar results are obtained in other contexts. However, this research adds to the increasing evidence that the impact of professor gender on the performance and academic decision-making of female students.

Read more:

• STEM-readiness and the gender gap in STEM at university
• Comparative advantage and the gender gap in STEM
• More on comparative advantage and the gender gap in STEM

Should fossils be treated like shipwrecks?

In a new article published in the journal Contemporary Economic Policy (ungated earlier version here), Paul Hallwood and Thomas Miceli (both University of Connecticut) discuss the law and economics of paleontological discovery - that is, fossil hunting. Hallwood and Miceli note that there are three groups of fossil collectors that have different incentives, in terms of the search for fossils and/or the recovery of scientific knowledge (the public value) from those fossils:

...professional paleontologists, commercial collectors who look to sell finds for a profit, and amateur collectors who do it out of interest rather than profit.

One important point is that recovering fossils leads to both public and private value:

Private good value is realized when the pecuniary value of a fossil is realized, or if it enters directly into a private collection; public good values are created when a fossil-type and the information associated with it are added to the stock of scientific knowledge in the field of paleontology.

In other words, there are positive externalities associated with recovering some (but not all) fossils. The problem with goods that have positive externalities is that, because the social benefit (what Hallwood and Miceli term the public good value) of recovery exceeds the private benefit (private value), private fossil hunters would engage in too little fossil hunting relative to the socially efficient (welfare maximising) amount of search. So, too few fossils would be discovered. On top of that, commercial collectors have little incentive to care about the scientific value of their finds, and so would not protect them in a way that preserves knowledge.

As a policy-maker, it may be tempting to try and capture the maximum public benefit by mandating that fossils must be given to museums or public academic institutions. However, that approach actually makes the problem of under-discovery worse, because then there is no chance of a private reward for recovery. On the other hand, having no restrictions on what happens to fossils after they are found would lead to more search and more fossils being found and excavated, but an inefficiently small amount of scientific knowledge being generated (because uncareful and low-cost excavation of fossils destroys much of the scientific value, which comes from their careful preservation in context). An example of this that I use in my ECONS102 class is when early palentologists paid Chinese peasants for each fragment of fossil they found. Unsurprisingly, the peasants found large fossils and then broke them up into smaller fragments, in order to earn a greater reward.

The article works through the various incentives mathematically and graphically, then looks at the current state of the law in the U.S., which could do with some improvement. Hallwood and Miceli conclude that:

Our analysis has shown that laws protecting scientific value are warranted based on the public good nature of fossil values, but this factor potentially creates an offsetting disincentive for profit-motivated collectors to engage in search, which is an essential prerequisite to recovery. Thus, if the scientific community needs to rely at least to some extent on private collectors to locate important fossils, there must be some recognition of the incentives that those searchers face. Federal legislation in fact pays little regard to this factor.

Their solution is interesting, but fairly intuitive:

...we believe there are lessons to be learned from the common law and state legislation pertaining to recovery of historic shipwrecks, which present many of the same economic issues.

As they note in one of the footnotes to the paper, in relation to the recovery of shipwrecks:

...the admiralty courts aim to balance the recovery of private (treasure) values and public (scientific archaeological) values from sunken wrecks. Neither is prioritized over the other. Second, property rights to work over sunken wrecks are granted to private companies working on federal (submerged) lands. Third, the admiralty courts promote the collection of sound archaeological knowledge from a historic shipwreck through two devices: (1) there is variation in the percentage of treasure value retained by a salvage company depending on the quality of work performed; and, (2) in cases of poor or nonexistent archeological work, applications for permits in the future can be denied.

So, it seems that, in theory at least, we possibly should treat fossils like shipwrecks, if we want both the optimal amount of search for fossils and the recovery of the optimal amount of scientific knowledge. 

In the battle between theories of sex, the red queen hypothesis dominates

I recently read this 2017 article by Motty Perry (University of Warwick), Philip Reny (University of Chicago), and Arthur Robson (Simon Fraser University), which seemed like a fairly random addition to an issue of The Economic Journal (open access). I say random because the title is "Why sex? And why only in pairs?", and the paper details a mostly theory-driven explanation (along with some simulation results) of why reproductive sex occurs between couples, and not between three or more parents. Given that there is a Journal of Mathematical Biology, The Economic Journal seemed like an odd fit to me.

Nevertheless, this was an interesting paper to read. Perry et al. outline attempt to unravel the following puzzle:

The breadth and variety of methods by which different species reproduce through sex is nothing short of remarkable. Nonetheless, sexual reproduction displays a stunning regularity. We can state that:

Each sexually produced offspring of any known species is produced from the genetic material of precisely two individuals. That is, sex is always biparental.

The obvious, but overlooked, question is, why? In particular, why are there no triparental species in which an offspring is composed of the genetic material of three individuals?

They first note that:

...a complete theory of sex must strike a delicate balance. On the one hand – as is well known – it must explain why genetic mixing is sufficiently beneficial so that biparental sex overcomes the twofold cost of males it suffers because an equally sized asexual population would grow twice as fast (Maynard Smith, 1978). On the other hand – and this point is central here – genetic mixing must not be so beneficial that a further increase in fitness would be obtained from even more of it through triparental sex.

They then outline the two main competing theories: (1) the mutational hypothesis; and (2) the 'red queen' hypothesis. The mutational hypothesis contends that sex is advantageous (compared with asexual reproduction) because "it halts the otherwise steady accumulation of harmful mutations". In contrast, the 'red queen' hypothesis contends that each species is in a constant battle with parasites (or other dangerous organisms), and asexual reproduction, where each offspring is genetically identical to the parent, is highly vulnerable to extinction at the hands (or tentacles, or whatever) of a new parasite evolved to attack the specific genetic makeup of the species.

The problem with sexual reproduction (when compared with asexual reproduction) is the so-called 'two-fold cost of sex':

...that a sexual population with a one to one ratio of (unproductive) males to females produces half as many offspring as an equally sized asexual population... The simple reason for this is that every individual in the asexual population can reproduce whereas only half of the individuals in the sexual population – the females – can do so.

Now, a successful theory of sexual reproduction must explain why biparental sex is advantageous over asexual reproduction. However, it must also explain why triparental sex is not even more advantageous.

Using a fairly simple narrative approach, supported by a minimum of necessary mathematical detail. Perry et al. go on to show that:

Under the mutational hypothesis, triparental sex always dominates biparental sex and high genomic mutation rates only serve to increase this advantage. With all three options available, either asexuality would be best or triparental sex would be best. Accordingly, biparental sex should not be observed.

In contrast, there is a ray of hope with the red queen hypothesis. Using a deliberately simplified red queen model, we have shown that biparental sex can have even an overwhelming advantage over asexuality, yet there is no further gain from more than two parents.

So, there you have it. The (coolly-named) red queen hypothesis seems to be the winner.