Suddenly, We Don’t Have Enough People
Just a generation or so ago, a book entitled The Population Bomb, by Paul Ehrlich, sold millions of copies, continuing a long tradition of Malthusian doomsday forecasts. Ehrlich predicted that the world would soon be overpopulated, resulting in mass starvation and death. But the dire predictions did not come to pass. Instead, we face a new and greatly underappreciated risk: population collapse.
There is a long history of Malthusian doomsdaying. The term itself is derived from the name of Thomas Robert Malthus, who at the beginning of the 19th century, famously theorized that since the population grew geometrically while food output grew linearly, mass starvation was an inevitable outcome for much of humanity.
Malthus made this prediction at a time when the population had just crossed 1 billion. Ehrlich’s book was released in 1968, by which time the population had more than tripled, yet no worldwide famines materialized. On the contrary, the global population has since more than doubled again, to some 8 billion people. Meanwhile, the global incidence of hunger and the frequency and severity of famines has declined dramatically.
Malthusian reasoning appears sound enough, so why were these forecasts so wrong? There are a number of factors to consider, but the first among them is that Malthusians missed the mark on fertility, or the number of children born per woman. Instead of remaining constant, it steadily declined as countries developed and living standards improved.
In times past, it was accepted that a large fraction of children would not live past the age of five. Families preferred to have many children as a kind of “insurance” for their old age. But economic/technological development greatly reduced child mortality rates worldwide. Meanwhile, growing opportunities for women in the workforce raised the opportunity cost of having children.
As a consequence, the global fertility rate peaked around 1965, at just over 5 children per woman. Since then, it has been in steady decline and is now down to just 2.3. Note, a fertility rate of 2.1 is considered to be the minimum threshold…