The Trap, and How It Broke

Thomas Malthus published his essay in 1798, and the argument in it is simple enough to state in a sentence. Population, unchecked, grows geometrically. The food supply grows arithmetically. So any improvement in output is eaten by extra mouths, and living standards return to subsistence.

For almost the entire history of the species this was true. Better ploughs, new crops, drained marshes and improved rotations all produced the same result: more people rather than richer people. A good century raised the population and the next generation was no better fed than the last. Economic historians call it the Malthusian trap, and the striking thing about the pre-1800 income series is how flat they are across enormous technological change.

The Black Death is the cleanest demonstration, because it ran the mechanism backwards. A third or more of Europe died, the land did not, and the survivors found themselves with more of it each. Real wages rose sharply, the labouring classes ate meat, and the English Parliament passed a Statute of Labourers in 1351 attempting to fix wages at pre-plague levels, which failed, because you cannot legislate against arithmetic. Then population recovered over the following century and the gains disappeared. Nobody chose either outcome.

Malthus is routinely quoted as though he welcomed famine, and the text does something closer to the opposite. He distinguished positive checks, which raise the death rate (famine, disease, war) from preventive checks, which lower the birth rate, chiefly through later marriage. He thought only the second was humane and recommended moral restraint. What he could not imagine was a third possibility, which is the one that happened.

The timing is the part worth dwelling on. He published within a few decades of sustained productivity growth beginning in Britain, and he was describing a constraint at the moment it started to move. Two things then had to happen, and neither had been available to any previous society. Output per worker had to keep rising rather than rising once, which required continuous technological change. And births had to fall, which required a set of social changes (children surviving, schooling costing money, pensions replacing sons as old-age security, women in paid work) each of which takes a generation.

So the standard verdict is that Malthus was wrong, and the more useful verdict is that he was right about everything he could see and wrong about the future. He had the best available evidence, the longest possible run of data, and a real mechanism. What defeated him was a change in the rate of technological progress that nothing in the record could have signalled.

That makes his case the permanent reference for a particular kind of argument: this constraint has held for the whole of recorded history, therefore it will hold. Such arguments should not be dismissed (the evidence behind them is usually excellent) and they should not be accepted either. The right response is to ask what would have to change for the constraint to move, and how likely that is. Malthus never asked it, because in 1798 there was nothing in the record to suggest that anything could.