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My latest Mind and Matter column in the Wall
This Halloween, the United Nations declared over the summer, a
baby will be born somewhere on Earth who will tip the world's
population over seven billion for the first time. Truly do
international bureaucrats have the power of prophecy!
The precision is bunk, of course, or rather a public-relations
gimmick. According to demographers, nobody knows the exact
population of the world to within 100 million. (Incidentally, the
record-setting baby will not be the seven billionth human being to
have existed, as some press reports have implied-more like the 108
John. S. Dykes
Nonetheless, the occasion will provide an excuse for yet another
round of Malthusian gnashing of teeth about overpopulation. But we
shouldn't let it obscure the real story of the past 50 years, which
is not how much faster than expected, but how much slower,
population has been growing.
In the 1960s, some experts feared an exponentially accelerating
population explosion, and in 1969, the State Department envisaged
7.5 billion people by the year 2000. In 1994, the United Nations'
medium estimate expected the seven-billion milestone to arrive
around 2009. Compared with most population forecasts made in the
past half century, the world keeps undershooting.
The growth rate of world population has halved since the '60s
and is now expected to hit zero around 2070, with population around
10 billion, though some news outlets prefer to focus on the U.N.'s
"high" estimate that it "could" reach 15 billion. The truth is,
nobody can know, but if it's below 10 billion in 2100, we will have
only increased in numbers by 1.5 times in the 21st century,
compared with a fourfold increase in the 20th.
This "demographic transition" to lower birth rates began in
Western Europe in the 19th century and later spread to North
America, then Latin America, Asia and now Africa. In 1955, the
birth rates per woman in Yemen, Iran, Bangladesh, Nigeria, Brazil
and China were, respectively, 8.3, 7.0, 6.8, 6.5, 6.1 and 5.6.
Today they are 5.1, 1.7, 2.7, 5.2, 1.8 and 1.7. Notice: The poorer
a country has remained, the slower the fall.
The fall in the birth rate is a largely voluntary phenomenon. It
has happened just as fast in countries with no coercive population
policy as it has in China, with its Draconian two-child law. The
demands for coercion that were common in the 1970s-"Why should the
law not be able to prevent a person from having more than two
children?" wrote Paul Ehrlich, Anne Ehrlich and John Holdren in
1977-seem embarrassing in retrospect.
Birth rates have gone down because of prosperity, not poverty.
Everywhere it has occurred, it has followed a fall in child
mortality and famine and an increase in income and education. The
wider availability of contraception has been necessary, even vital,
for this shift, but it has not been sufficient.
John S. Dyke. To a biologist, the demographic transition is
both surprising and intriguing. No other species drops its birth
rate when its food supply increases. Frankly, no expert has yet
fully explained the phenomenon. It remains something of a
The best guess is that modern society causes human beings to
switch their reproductive strategy from quantity to quality. Thus,
once child mortality drops and paid work becomes available to the
children of subsistence farmers, parents become more interested in
getting one or two children into education or jobs than in
begetting lots of heirs and spares for the farm.
Whatever the explanation, history shows that top-down policies
aimed directly at population control have generally proved less
successful than bottom-up ones aimed at human welfare, which get
population control as a bonus. The faster poor countries can grow
their economies, the slower they will grow their populations.