Since You Asked

Malthus’s ghost and baby number 7bn

“In five days, world population is projected to reach 7 billion.” – UN Population Fund, October 26

There will be 7bn of us come Halloween? You’re kidding.

Someone at the UNPFA has a sense of humour, it seems. This is a terrifying prospect to some and cheery for others, while most of us find it irrelevant. Halloween seems appropriate.

This is a statistical projection, and statistical projections don’t have a sense of humour.

But they do have margins of error. The UNPFA doesn’t even know whether the seven billionth person will be born in 2011. Even the UK is currently relying on 10-year old census data. There are places in the world where the data are decades old and we’re just guessing at the population. Still, such celebrations – if they are celebrations – do pass the time.

Time does fly, doesn’t it? When I was at school I was told there were only 5bn people in the world.

In the mid 1980s, there were only 5bn. The world’s six billionth person – officially Adnan Nevic of Sarajevo, although of course we have no idea who it really is – is only about 12 years old.

Each new billion comes more swiftly than the last one – it’s pretty worrying.

Actually, population growth has been slowing. It grew by a third between 1960 and 1974 – from 3bn to 4bn – but it’s taken more than 21 years to grow by a third from about 5bn to 7bn. The UN has a projection – the “low fertility” scenario – where the world population briefly tops 8bn then starts falling.

So Malthus was wrong?

Even Robert Malthus realised that there was such a thing as birth control. His more excitable successors, such as Paul Ehrlich, author in 1968 of The Population Bomb, have been fairly thoroughly rebutted by subsequent events. Dan Gardner, author of the fascinating Future Babble, summarises Ehrlich’s three scenarios for the 1980s as “everybody dies” (starvation-triggered nuclear war), “every third human dies” (starvation-triggered virus) and in the optimistic scenario “a billion people still die of starvation”.

Poor Ehrlich. Maybe next decade … What about Malthus?

He’s harder to judge: his most famous argument is actually rather abstract. He argued that unchecked population growth is exponential: 2, 4, 8, 16, 32, 64. Progress in agricultural production can only be arithmetic at best: 10, 20, 30, 40, 50, 60. Eventually, the exponential always catches up and overtakes the arithmetic progress. Sooner or later, then, the population bumps up against our ability to feed everyone.

And mass starvation ensues.

That’s possible. More likely is that the availability of food keeps limits to population growth. In a “Malthusian economy” living standards never improve beyond subsistence, no matter how much technological progress there is, because population always keeps pace with the growth of the economy.

Which is nonsense, of course.

Which is a surprisingly good description of human existence until, roughly, 1798, which is when Malthus’s famous Essay on the Principle of Population was published. Calorie intake of rural labourers in England seems to have been somewhat less than it is in primitive hunter-gatherer societies today. Happily for humanity but unfortunately for Malthus subsequent developments were a big surprise: agricultural productivity dramatically surged ahead of population.

Does that mean we’re all fine?

It means “so far, so good”. Some experts think that natural resource scarcity has to catch up with us eventually. A more optimistic school of thought argues that large populations mean more good ideas to go around. We’ll innovate at an ever-faster rate and solve whatever energy, resource or environmental problems come our way. The optimists have been right for a couple of hundred years.

Nothing to worry about, then.

Not quite. The modern Malthusians were looking very foolish in the 1990s: the price of skilled labour was rising inexorably and the price of most commodities, notably oil, was low. But in recent years there’s been a distinct rise in these prices. Perhaps this is a temporary thing: the rising prices could spur energy-saving innovations. Or perhaps Malthus’s ghost will come back to haunt us, even if not this Halloween. It’s hard to say: population growth is a funny thing. Malthus himself had three children – but no grandchildren.

Also published at ft.com.

29th of October, 2011Since You Asked • Comments off