Back before the good ‘ol days, even before there was an Old West, everyone was stuck in what’s called a Malthusian trap. The idea is that because technological innovations happened so rarely, people’s reproductive proclivities made sure that any technological advances would just translate into more people. If you invent a new plow that made land twice as productive, you’d produce more food and thus you could feed more people. People would go about making more of themselves in short order and in the end, you’d end up with just as much food per person as before the invention. The average person gets no richer.
The first part of Clark’s book is basically a long discussion of what are the implications of Malthusian trap. One of them, that many find perverse, is the idea that bad things like repeated droughts and persistent diseases are actually good things. Because they increase the death *rate*, they improve the average amount of food per living person.
Bryan Caplan thinks Prof. Clark is misinterpreting bad things. Instead of changing the relationship between the death rate and income per person, droughts and harvest failures reduce the productivity of workers. ((Go to Caplan’s post for pretty pictures, if such is your bag.))
[T]he effect of harvest failures in the Malthusian model is to reduce income, which causes starvation, which reduces population, until you eventually get the old level of per-capita income with a new, lower population.
Ok. Fine. There’s two objections to Caplan’s interpretation of harvest failures. First, what does he mean by bad harvests “kill people by making a given number of people less productive”? Less productive at what? The economy was almost completely agrarian in these societies, so a bad harvest makes people less productive at making food. If you’re eating close to subsistence, less food means starving to death. This sounds like a change in the death schedule to me.
Second, and more substantive, Clark isn’t talking about supply shocks. He’s talking about persistent petulances and plagues. Introduce a new disease, and yes you get a one time decline in productivity which temporarily reduces incomes, but the long run effect is to increase the death *rate*.
For example, introduce malaria into a population and it makes everyone much less productive. This is bad in the short run as less food can be produced. Slowly, as people die from the disease, the total population decreases and the amount of food per person goes back to its original level. However, because malaria is still around, the rate at which people die goes up. By Clark’s reasoning, this has the effect of increasing the food per person. In the long run, then, the effect is an unmitigated good. Malaria increases the food per person.
Sick isn’t it.
UPDATE: Yeah, I passed my exam! Clark (on Caplan’s site): “What Caplan has done in redrawing the figure his way is to assume that extra disease has no effect on the death rate at a given material living standard. But this is just to assume away the possibility that the death schedule could change. Now that is a pretty strong assumption, and one demonstrably untrue.” That’s what I said! Except, well, he said it much better.