To start the book Greg lays out his central claim that most of human history can be explained by a Malthusian model. By this he means that changes in birth and death rates are the means of changing the real wage in the long run. He also suggests it is very hard to raise living standards in the long run, again short of leaving Malthusian conditions, as England later did.
These pages contain some of the book's most important material. If Clark is right, one relatively simple model can explain a great deal of human history.
From reading his book, I've upped my attachment to the Malthusian model from p = 0.2 to p = 0.37; that's a big shift and it's to Clark's credit. But I am still not convinced or even at p = 0.5, and here is why...
1. Did hunter-gatherers really have living standards as high as people in 18th century England? By focusing on the long run, Clark neglects the pains of equilibration. Hunter-gatherers who survived to 30 maybe had decent lives, but population was very low. It was kept low, in part, by lots of brutal and painful death. We can’t just focus on the steady-state conditions in making welfare comparisons. Modern research is also discovering that primitive societies have very high levels of war and violent death; if we’re playing time travel games, I’m opting for 1800, and not just to have a chance of hearing Haydn. I’ll also take modern Tanzania over the hunter-gatherers, in a heartbeat, contra what Clark implies.
2. Why should we aggregate income comparisons by country (or the whole world) rather than by city? World history looks very different if we do the latter. Aren’t most countries relatively recent inventions anyway? More generally, I would like a more disaggregated look at the data. Big chunks of the urbanized human population — pre 1800 — seem to have violated Malthusian precepts for centuries on end. "Stadtluft macht frei" was the old German saying.
3. How long is the long run? This is one of my biggest questions about the work and about Malthusian predictions more generally. Are we just comparing 30,000 B.C. to 1800 A.D.? If so, we have only two data points. If we look at times in between, there is much more scope for non-Malthusian results, even if they hold for "only centuries."
4. Violent conflict and predation are not given enough (any?) importance. Cities that avoid violent conflict do pretty well. Admittedly, violence is itself endogenous to Malthusian considerations, but I’m not going to reduce war to population pressures (and certainly Clark never tries to.) Isn’t part of the historical inability to boost long-run living standards simply the result of recurring wars and depredations? 17th century European history, among other times, shows just how much war matters.
5. Should I reject the Julian Simon model I grew up with? In that view there are increasing returns to scale within cities, where people usually don’t starve. The countryside languishes in poor countries, in part because it is underpopulated. Rather than having a "one population model" with an aggregate "n," labor markets are local. The "plagued by diseconomies of scale rural folk" cannot sufficiently connect with the "economies of scale urban sophisticates," mostly because of bad institutions and backward infrastructure. And the cities prove unable to protect themselves against all ongoing predations. Doesn’t that model fit the data too, and fit the disaggregated and shorter-run data better?
6. I can’t find the single place where Clark directly tests the Malthusian model. I fear he will regard this observation as unfair, since there is argumentation and data of some kind on virtually every page. But I still am not satisfied. I see lots of evidence for "history shows mean-reversion and population pressures are one factor affecting wages." It is harder to find a) what "best alternative" the Malthusian model is being tested against, b) what evidence would adjudicate between models, c) what is the short-run claim about the response of population to real wages, and d) what in history are the "hard cases" for the Malthusian model and how does Clark handle them?
7. Charles Kenny argues that the Malthusian model does not explain observed short-run dynamics for population and real wages. I don’t regard this piece as a refutation of Clark by any means, but the evidence on how well real wages predict population growth seems to me murky rather than decisively in Clark’s favor. There’s just not a single, simple model at work here.
If you are coming to the book blind, here is a short piece by Clark. Here is my earlier column on the manuscript. Here is a survey paper on the Industrial Revolution and the Malthusian trap. Here is more good background. Peter Lindert considers how much real wages predict population growth in British history. Read this too.
What do you all think?