The Population Mystery

Despite the doomsayers, past and present, the world’s population has grown and will grow:


Estimates for 10,000 B.C. through 1940 derived from U.S. Census Bureau, “Historical Estimates of World Population” (left column). Estimates for 1950 through 2050 derived from U.S. Census Bureau, “Total Midyear Population for the World: 1950-2050.” Intervals between years are irregular because of variations in the intervals in the Census tables.

Is it possible that the world’s population will reach an unsustainable level, after which it must shrink and/or plunge the world into abysmal poverty?

Donald Boudreaux, in a 2008 post, writes:

In his new book, Common Wealth, Jeffrey Sachs expresses his concern about population growth.  Worried by a U.N. prediction that global population will rise to 9.2 billion by the year 2050, from 6.6 billion today, Sachs says (on page 23 of his new book) the following about these additional 2.6 billion persons:

I will argue at some length that this is too many people to absorb safely, especially since most of the population increase is going to occur in today’s poorest countries.  We should be aiming….to stabilize the world’s population at 8 billion by midcentury.

Eight billion.  I’m not sure where Sachs got that number.  And, to be frank, I’m not curious about where he got it….

A … problem with Sachs’s eight-billion number is that, in calculating it, there is no way to predict how human creativity will alter the world during the next 42 years.  It’s ludicrous to pretend that we can know now what, say, the average MPG will be for internal-combustion engines in 2050.  Hell, we don’t even know if automobiles and lawnmowers and the like will still use such engines then.

Will another Norman Borlaug arise, between now and 2050, to spark another green revolution?  Will someone invent a way to efficiently power automobiles with air?  Will someone develop new and better techniques for defining and enforcing private property rights in ocean-going fish stocks so that the tragedy of the commons called “over-fishing” is eliminated?  Will an enterprising entrepreneur invent a means for ordinary households to power their homes with mulch or autumn leaves or small fragments of fingernail clippings?

Think back 42 years to 1966.  Who in that year imagined personal computers in nearly every home in America?  The Internet?  Digital cameras?  Cell phones?  Quality wines sold in screw-top bottles?  Buying music with literally the click of a button (and not having to burn fossil fuels in driving to the record store).  Aluminum cans that contain only a fraction of the metal that cans contained back then?  The Kindle (that will reduce the number of trees cut down to enable people to read books)?  Medical advances that make hip-replacements about as routine as getting cavities filled by the dentist?  Microfiber?

There is no way — literally, no way — to know how technology and social institutions will change between now and 2050.  Given this impossibility — and given the fact that we can nevertheless predict with confidence that technology will advance and that social institutions will change — to assert that “optimal” population in the year 2050 will be eight-billion persons is ludicrous in the extreme.  It’s faux-science, and deserves only ridicule.

Here’s Bryan Caplan, writing today:

I finally got around to reading Matt Ridley’s The Rational Optimist. Highlights….

2. How non-renewable energy is more abundant than renewable energy:

The Atlantic Ocean is not infinite, but that does not mean you have to worry about bumping into Newfoundland if you row a dingy out of a harbour in Ireland.  Some things are finite but vast; some things are infinitely renewable, but very limited.  Non-renewable resources such as coal are sufficiently abundant to allow an expansion of both economic activity and population to the point where they can generate sustainable wealth for all the people of the planet without hitting a Malthusian ceiling, and can then hand the baton to some other form of energy.

3. The fallacy of pessimistic extrapolation:

[T]he pessimists are right when they say that, if the world continues as it is, it will end in disaster for humanity.  If all transport depends on oil, and oil runs out, then transport will cease.  If agriculture continues to depend on irrigation and aquifers are depleted, then starvation will ensue.  But notice the conditional: if.  The world will not continue as it is.  That is the whole point of human progress, the whole message of cultural evolution, the whole import of dynamic change – and the whole thrust of this book….

5. Declining flu mortality is not dumb luck.

The modern way of life, with lots of travel but also rather more personal space, tends to encourage mild, casual-contact viruses that need their victims to be healthy enough to meet fresh targets fleetingly…

[W]hy then did H1N1 flu kill perhaps fifty million people in 1918?  Ewald and others think the explanation lies in the trenches of the First World War.  So many wounded soldiers, in such crowded conditions, provided a habitat ideally suited to more virulent behaviour by the virus: people could pass on the virus while dying….

The main argument I wish Ridley pursued more: How the very existence of civilization creates a mighty presumption against pessimism in all its forms.  But I view his omission optimistically: The arguments for optimism are so numerous that no one book can contain them all.

Doomsayers are simple-minded extrapolators. I suspect that they have an aesthetic objection to population growth, which they wrap in pseudo-scientific garb. Like their close kin, anti-market politicians and pundits, doomsayers seem to have no conception of the power of human ingenuity to make life more livable — when that ingenuity is not stifled by government.

Related posts:
The Causes of Economic Growth
A Short Course in Economics
Addendum to a Short Course in Economics
The Price of Government
The Price of Government Redux