It would have been Norman Borlaug's 100th birthday today. When I think about Borlaug it always makes me appreciate the work of Malthus. A lot of people find that odd, but I think it's because of the low quality of critiques of Malthus floating around.
What's frustrating about critiques of Malthus is that Malthus openly admits that the subsistence constraint is differentially binding because agriculture is differentially productive. He does have the famous base case model with arithmetic growth of food and geometric growth of population. And that's gripping for people, and the specification may be all wrong. But it served the useful purpose of being an equilibrium model (and an equilibrium model used by the rest of the classical economists, I should add). It also served the purpose of succinctly demolishing Condorcet and the utopians. Malthus insisted that you could not depend on the perfectibility of man. Man is an animal and the study of man needs to be tethered to that fact. We social scientists are studying a particularly goofy, creative, and eccentric primate that occupies a particular ecosystem, and those facts will govern the science of man. Moreover, when Malthus applies his model he talks about variations in preventative checks, positive checks, and agricultural productivity across different societies. I have not read much in his Principles of Political Economy outside of the stuff on general gluts, but I would be surprised if he denied technological progress there. So he is very clear that these parameters vary and change, but the fundamental point - and the point of having the rigidly parameterize arithmetic/geometric model - is that generally speaking man is constrained by the resources that sustain him.
Norman Borlaug matters precisely because Malthus was right on this point. If Malthus was wrong, Borlaug would not deserve his Nobel.
Accepting Malthus as one of the great political economists should really not be that hard. If you're willing to think in terms of early 18th century equivalents (i.e. - changing around what is the output and what is the input exactly), if you're willing to take logs, and if you squint a little, Malthus's model is basically the Solow model. Same sort of structure and same sort of equilibrium with the same sort of conclusion. Solow gets some abuse, sure, but nothing like the stupid sort of critiques that Malthus gets. Could you imagine someone offering "Solow is wrong because there's technological development" as a serious critique?
If you want to take the unified growth theory route and just label periods where subsistence constraints are binding as "Malthusian" and when they're not as "non-Malthusian" it makes perfect sense why you would use those sorts of labels. But don't try to pass off that labeling schema as history of economic thought.
What do we fault Solow for? Well we wish he endogenized a few things, chiefly technological growth. But even without that work, Mankiw, Romer, and Weil show that you can get a lot of mileage out of the Solow model. And of course "better" models cannibalize the Solow model for spare parts. The same could certainly be said for Malthus. It would be nice if he had more on technological growth. But don't confuse that case of "more research required" with the case that the model is useless or doesn't illustrate an important point. Anyway, my point here is that when Solow gets critiqued it makes for a quite edifying read. Not so with critiques of Malthus.
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