Less productive at what?

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.

4 thoughts on “Less productive at what?”

  1. Is this phenomenon something that shows up on the longer run (like on the scale of decades or centuries), or is it visible in the short term? Is there a minimum population threshold for this effect?

    This argument has probably been brought up, but this effect seems simplistic in the face of job specialization. Lose an unskilled laborer or a child to the plague, and the productivity of your settlement goes down a little. Lose your skilled blacksmith or carpenter, and you’re in much more trouble. I guess that isn’t as much of a problem in a larger settlement with some built-in redundancy. It still seems as though there’s a maximum number of losses that a group can absorb before they wind up in a death spiral.

  2. Yeah it takes a while, maybe 3-4 generations, for these transitions to take place. See Clark’s discussion of the plague in post I linked to in the update.

    Your second paragraph makes a good point. That said, dead blacksmiths or the loss of the blacksmithing skill in a Malthusian society reduces the level of technology in society. The net effect of technology shifts in these societies is zero after a couple generations. Income levels go back to their original levels.

    This is exactly why Malthusian economies are so damned weird…

  3. So “Malthusian” (yeah I get the reference) is another way of saying that a society has reached a dynamic equilibrium for their environment and social structure?

    I guess, considered over a few generations, the loss of skilled artisans is negligible unless the society was on the edge of collapse anyway.

    Amazing what you can learn from a few games of Civ =)

  4. Malthusian is a particular social environment where there’s a stable relationship between the number of deaths and the income per person. Basically, the higher the income, the lower the number of deaths. Because the birth rate is more or less fixed (women can only have so many babies), when incomes increase the number of deaths is less than the number of births and the population increases. When the population increases income per person goes down.

    Equilibrium is a state the economy is in. In the Malthusian environment, equilibrium is the level of income where the death rate equals the birth rate. Small deviations away from the equilibrium (a bumper crop of babies or something) result in the economy just returning to the equilibrium.

    In this Malthusian economy, technology advances or declines don’t effect the standard of living in equilibrium. Its this feature that makes a Malthusian equilibrium different than a modern one.

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