Thursday, January 13, 2011

The Malthusian Malady

Of the writers who can safely be called much quoted but little read, the economist/philosopher T.R. Malthus sits near the head of the list. The basic argument of his Essay on the Principle of Population is known to everyone given rise to a whole school of pessimistic futurists, the Neo-Malthusians. But actually reading Malthus carefully (as I did for the first time recently) is very useful, and goes a long way to explaining why we never seem to arrive at the apocalyptic endgame that the essay, and Malthus's many successors, envision.

The argument that Malthus is known for is that rising population will strain the limits of the land, ultimately causing a crash of scarcity and famine--the so-called "Malthusian catastrophe." The conventional thinking now is that Malthus didn't anticipate the revolution in agriculture that would make it make it possible for the world to support a much greater population than it could in Malthus's time. But what's striking about going back to Malthus and his contemporary sources is not how little Malthus anticipated the future, but how slim the evidence was for his ideas in his own time.

Malthus's notion that population doubles in a generation was even stranger then than it seems now. Adam Smith estimated that the population of England doubled in roughly 500 years. Malthus supports his claims for a faster increase with some numbers from the German demographer J.P. Sussmilch. These come mainly from a chart that showed the population of the duchy of Pomerania doubling in about 60 years, which were followed by a period of epidemics and decline.

Sussmilch himself, however, did not subscribe to a theory anything like Malthus's. Actually, the opposite: Sussmilch believed (and I get this from a turn of the century English summary, little of Sussmilch's work has been translated into English, though you can get the original on Google books or get a sense of it here) that the world could support as many as 5 billion people. And note that this in 1761.

Was Malthus aware of this? Maybe not directly. He had cribbed Sussmilch's data from the summary of another English writer, the philosopher statistician and philosopher Richard Price, who included them in his Observations on Reversionary Payments (a fascinating early work on the demographics and economics of pensions). But this doesn't get Malthus a pass, because Price also didn't think those numbers backed anything like a Malthusian theory of population. On the contrary, Price believed that the population of England was ...  falling.

Price didn't think that drop was caused by anything like a Malthusian cycle of famines. He attributed it to to miserable urban conditions--Price provides some still heartbreaking numbers on lifespan and infant mortality in the cities of the time. On his populations estimates, which he got from tallies of housing stock, Price was probably off-base. What really matters here, however, is that from Price's viewpoint, it was population decline, not geometric growth, that was a problem, one he urged the state to remedy by discouraging urban migration. Malthus certainly did know Price's position on this, and he must have known that Price would likely object to his misreading. Since Price was already dead, Malthus didn't need to worry about it.

So where did Malthus go so wrong? The problem, it seems to me, was that Malthus was not (unlike his modern followers) aiming to predict a future catastrophe. In later editions of his Essay, Malthus detailed objections to welfare policies, arguing that they would ultimately just exacerbate the population problem and cause more suffering. The concerns of his first edition, though. are not ordinary politics, but teleological, and he concludes with two chapters of theodicy that use his population theory to explain the inevitability of human misery.

Somewhat like the hapless Dr. Pangloss of Voltaire's Candide, who is convinced that we live in the best of all possible worlds, Malthus thinks we live in the only possible world. The population theory starts from the premise that the world we have, with all its misery, is the only one God could have made and works backwards to prove it. Malthus expanded the Essay into the giant work we have now, filling it with whatever numbers he could find to illustrate his theory. All this is just layers and layers of icing on the cake--as Malthus himself admits, the theory he builds in the first edition is really indebted to just a few books by four authors(Adam Smith and Richard Price among them ). Having constructed such an unimpeachable proof he manages to find, unsurprisingly, a limitless array of data and anecdotes to support it.

Inevitably, this makes Malthus an absolutely terrible futurist. The population theory is what Malthus himself would probably have called called a too-perfect model. A proof that explains why the world is exactly as it must be is a very bad template for explaining how it can change. Thus the problem for his latter day acolytes: having subscribed to a proof that explains so well why any improvement in our condition will have a disastrous downside, they are perpetually left saying that we just haven't gotten to it yet.

PS: It's worth giving a shout-out here to Google Books, without which a post like this would be impossible. The ability to go back easily to the original sources of someone Malthus without weeks of library research is really new, and hopefully you'll see a lot more people doing it.