More on the heights of nations (Are Africans really getting shorter?)

The height study has received a lot of press in the last few days. But Frances Woolley warns against taking its conclusions wholesale:

There is no data at all for people born before 1916. The first 20 years of “sprouting up” are generated by assuming that the 1896 to 1916 period was characterized by the same kind of increase in height as later periods. The data for the people born just after 1916 comes from surveys carried out in 1998 or later – i.e. from measurements of the heights of people up to 80 years old. To estimate the average height, at age 18, of people born in 1918 by observing that cohort in 1998 when they are 80 years old involves some heroic assumptions – assumptions about shrinkage with age, survival rates, etc. It would make a lot more sense to choose a shorter time span for the analysis, and give results that involved a bit less guesswork.

Is this bad science? I would say yes. It’s bad science because it oversells the results. The article overstates both the amount of height data the research team has (it’s not a century, in many cases it’s more like 50 to 75 years, especially for women), and also how recent the data is (in most cases the data is not for the 1996 birth cohort, but rather for earlier birth cohorts). It’s bad science because it presents headline grabbing results – and makes them readily available to journalists – without attempting to convey, in ways that are easy for reporters to understand, the amount of uncertainty associated with those results. Are Latvian women tall? Yes. Are they the tallest in the world? We can’t know that for sure unless we know the margin of error associated with the estimates of Latvian, Dutch, and other groups’ heights. It’s hard to put a standard error around the results of complicated projections – but that’s an argument against making complicated projections, and disseminating them to reporters, not against reporting standard errors.

More on this here.

H/T R. Briggs.

Demography is Destiny (or why two heads are better than one)

Bradford DeLong has a fantastic blog post on the relationship between population size and economic growth and development. He writes:

In Kremer’s model, population will grow and eventually population will be high enough that research and development will proceed fast enough to push income per capita high enough to trigger the demographic transition and thus break the Malthusian proportional link between resources and technology on the one hand and population on the other. After that link is broken, economic growth will predominantly take the form not of Malthusian increases in population but rather Industrial Revolution and Modern Economic Growth increases in living standards and labor productivity.

The breakthrough to an Industrial Revolution, Modern Economic Growth, and our present prosperous global post-industrial economy is therefore baked into the cake. It is an all-but-inevitable event in human history produced by the simple fact that when it comes to generating useful ideas two heads are better than one: “the fundamental nonrivalry of technology as described by Paul Romer (1986)…”

DeLong then tests an alternative theory in which the economic takeoff of WENA countries after 1750 could have been a fluke, and concludes that the British industrial revolution at most saved the world 150 years — that is, “if you take the association between global populations and global economic growth back before the British Industrial Revolution seriously, as a causal relationship.

The whole post is worth reading. The empirical bits are clear and easy to follow. See also here.

In my Political Economy of Development class I make sure that my students understand the relationship between demography and human development — (i) the impact of demography on state development; and (ii) the impact of state development on markets and economic growth and development. To that end I often use these three illustrations.

Up until the mid 1990s tiny Europe had more people than all of Africa. In the next 30 years Africa’s population will grow by about 800 million people. By 2050 the Continent is projected to have 2 billion people; and half of the children being born in the world will be African. There is no reason to believe that the African experience after these demographic changes will not follow established correlations between population size, state development, and technological change.

Why are Africans getting shorter?

South Asia still posts the lowest average height for adults in the world (see image below). But a remarkable finding of a recent study is that adult Africans (among other low income regions of the world) have gotten shorter, on average, since the 1970s.

Being taller is associated with enhanced longevity, and higher education and earnings. We reanalysed 1472 population-based studies, with measurement of height on more than 18.6 million participants to estimate mean height for people born between 1896 and 1996 in 200 countries. The largest gain in adult height over the past century has occurred in South Korean women and Iranian men, who became 20.2 cm (95% credible interval 17.5–22.7) and 16.5 cm (13.3–19.7) taller, respectively. In contrast, there was little change in adult height in some sub-Saharan African countries and in South Asia over the century of analysis. The tallest people over these 100 years are men born in the Netherlands in the last quarter of 20th century, whose average heights surpassed 182.5 cm, and the shortest were women born in Guatemala in 1896 (140.3 cm; 135.8–144.8). The height differential between the tallest and shortest populations was 19-20 cm a century ago, and has remained the same for women and increased for men a century later despite substantial changes in the ranking of countries.

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What explains deceleration in average adult heights on the Continent?

One obvious explanation is a decline in nutrition amid rising populations and declining agricultural productivity (Africa barely registered a green revolution). Another major culprit is the economic disaster that visited the Continent from the late 1970s to the early 1990s — which resulted in poor nutrition and an unchecked disease burden. Lastly, there is the issue of water and sanitation, especially in the context of a rapidly urbanizing population, which has direct implications for the realized disease burden.

The top 20 best countries to invest your money in Africa

This is according to the latest Ernst & Young’s Africa Attractiveness Report (2016). Kenya is ranked 4th. Ahead of Tunisia, Mauritius, and Botswana. You just need to spend a few hours in Nairobi, or the other 46 county headquarters, to understand why. While economic inequality remains to be a huge (political) challenge, it’s hard to argue against the structural transformations underway in the Kenyan economy.

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More on this year.

Human Capital and Economic Development in Britain, 1750-1930

B. Zorina Khan writes:

Many argue that the nature of early British industrialization supports the thesis that economic advances depend on specialized scientific training, the acquisition of costly human capital, and the role of elites. This paper examines the contributions of different types of knowledge to British industrialization, by assessing the backgrounds, education and inventive activity of the major contributors to technological advances in Britain during the crucial period between 1750 and 1930. The results indicate that scientists, engineers or technicians were not well-represented among the British great inventors, and their contributions remained unspecialized until very late in the nineteenth century. For developing countries today, the implications are that costly investments in specialized human capital resources might be less important than incentives for creativity, flexibility, and the ability to make incremental adjustments that can transform existing technologies into inventions that are appropriate for prevailing domestic conditions.

…….. The patent records also enable us to examine whether a science background increased productivity at invention. Again, the patterns are consistent with the notion that at least until 1870 a background in science did not add a great deal to inventive productivity. If scientific knowledge gave inventors a marked advantage, it might be expected that they would demonstrate greater creativity at an earlier age than those without such human capital. Inventor scientists were marginally younger than nonscientists, but both classes of inventors were primarily close to middle age by the time they obtained their first invention (and note that this variable tracks inventions rather than patents). Productivity in terms of average patents filed and career length are also similar among all great inventors irrespective of their scientific orientation. Thus, the kind of knowledge and ideas that produced significant technological contributions during British industrialization seem to have been rather general and available to all creative individuals, regardless of their scientific training.

The whole paper is definitely worth reading and is available here.

Philip Tetlock lunches with the FT

As Tyler Cowen would say, the entire piece is self-recommending. Here are a couple of quotes from the exchange. Philip Tetlock is the author of Superforecasting: The Art and Science of Prediction.

Tetlock’s demonstration that strong commitment to theory or ideology makes poor forecasters — and that even best forecasts come to resemble guesswork when they reach more than a few years into the future — raises an unsettling possibility. It suggests that human affairs are mostly random and intractable. Incremental gains in foresight are possible, but there is no deep order to life…..

His work has taught him that everyone takes a heavy ideological endowment from their environment. “Any good political psychologist should have the moral and historical imagination to see how he or she could become almost any ideological creature that has existed, or does exist on the planet. That includes Nazis, Stalinists, Maoists, Isil . . . There but for the grace of God.”

More on Tetlock here.