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The
Population Surprise
by Max Singer
Will
the world's
population keep increasing as commonly believed? What are
the factors that account for its change? Please read the following
article and make out its viewpoints.
Fifty years from now the world's population
will be declining, with no end in sight. Unless people's values
change greatly, several centuries from now there could be
fewer people living in the entire world than in the United
States today. The
big surprise of the past twenty years is that in not one country
did fertility stop falling when it reached the replacement
rate─2.1 children per woman. In Italy, for example,
the rate has fallen to 1.2. In Western Europe as a whole and
in Japan it is down to 1.5. The evidence now indicates that
within fifty years or so world population will peak at about
eight billion before starting a fairly rapid decline.
Because in the past two centuries world population
has increased from one billion to nearly six billion, many
people still fear that it will keep "exploding" until there
are too many people for the earth to support. But that is
like fearing that your baby will grow to 1 000 pounds because
its weight doubles three times in its first seven years.World
population was growing by two percent a year in the 1960s;
the rate is now down to one percent a year, and if the patterns
of the past century don't change radically, it will head into
negative numbers. This view is coming to be widely accepted
among population experts, even as the public continues to
focus on the threat of uncontrolled population growth.
As
long ago as September of 1974 Scientific American published
a special issue on population that described what
had begun calling the "demographic transition" from traditional
high rates of birth and death to the low ones of modern society.
The experts believed that birth and death rates would be more
or less equal in the future, as they had been in the past,
keeping total population stable after a level of 10-12 billion
people was reached during the transition.
Developments over the past twenty years show
that the experts were right in thinking that population won't
keep going up forever. They were wrong in thinking that after
it stops going up, it will stay level. The
experts' assumption that population would stabilize because
birth rates would stop falling once they matched the new low
death rates has not been borne out by experience. Evidence
from more than fifty countries demonstrates what should be
unsurprising: in a modern society the death rate doesn't determine
the birth rate. If in the long run birth rates worldwide do
not conveniently match death rates, then population must either
rise or fall, depending on whether birth or death rates are
higher. Which can we expect?
The rapid increase in population during the
past two centuries has been the result of lower death rates,
which have produced an increase in worldwide from about thirty to about sixty-two.
(Since the maximum─if we do not change fundamental human
physiology─is about eighty-five, the world has already gone
three fifths as far as it can in increasing life expectancy.)
For a while the result was a young population with more mothers
in each generation, and fewer deaths than births. But even
during this population explosion the average number of children
born to each woman─the fertility rate─has been falling
in modernizing societies. The prediction that world population
will soon begin to decline is based on almost universal human
behavior. In the
United States fertility has been falling for 200 years (except
for the blip of the
),
but partly because of immigration it has stayed only slightly
below replacement level for twenty-five years.
Obviously, if for many generations the birth
rate averages fewer than 2.1 children per woman, population
must eventually stop growing. Recently the United Nations
Population Division estimated that 44 percent of the world's
people live in countries where the fertility rate has already
fallen below the replacement rate, and fertility is falling
fast almost everywhere else. In Sweden and Italy fertility
has been below replacement level for so long that the population
has become old enough to have more deaths than births. Declines
in fertility will eventually increase the average age in the
world, and will cause a decline in world population forty
to fifty years from now.
Because in a modern society the death rate
and the fertility rate are largely independent of each other,
world population need not be stable. World
population can be stable only if fertility rates around the
world average out to 2.1 children per woman. But why should
they average 2.1, rather than 2.4, or 1.8, or some other number?
If there is nothing to keep each country exactly at 2.1, then
there is nothing to ensure that the overall average will be
exactly 2.1.
The point is that the number of children born
depends on families' choices about how many children they
want to raise. And when a family is deciding whether to have
another child, it is usually thinking about things other than
the national or the world population. Who would know or care
if world population were to drop from, say, 5.85 billion to
5.81 billion? Population change is too slow and remote for
people to feel in their lives─even if the total population
were to double or halve in only a century. Whether world population
is increasing or decreasing doesn't necessarily affect the
decisions that determine whether it will increase or decrease
in the future. As the systems people would say, there is no
feedback loop.
What does affect fertility is modernity. In
almost every country where people have moved from traditional
ways of life to modern ones, they are choosing to have too
few children to replace themselves. This is true in Western
and in Eastern countries, in Catholic and in secular societies.
And it is true in the richest parts of the richest countries.
The only exceptions seem to be some small religious communities.
We can't be sure what will happen in , because few of them have become modern
yet, but so far it looks as if their fertility rates will
respond to modernity as others' have.
Nobody can say whether world population will
ever dwindle to very low numbers; that depends on what values
people hold in the future. After the approaching peak, as
long as people continue to prefer saving effort and money
by having fewer children, population will continue to decline.
(This does not imply that the decision to have fewer children
is selfish; it may, for example, be motivated by a desire
to do more for each child.)
Some people may have values significantly
different from those of the rest of the world, and therefore
different fertility rates. If such people live in a particular
country or population group, their values can produce marked
changes in the size of that country or group, even as world
population changes only slowly. For example, the U.S. population,
because of immigration and a fertility rate that is only slightly
below replacement level, is likely to grow from 4.5 percent
of the world today to 10 percent of a smaller world over the
next two or three centuries.Much
bigger changes in share are possible for smaller groups if
they can maintain their difference from the average for a
long period of time. (To illustrate: Korea's population
could grow from one percent of the world to 10 percent in
a single lifetime if it were to increase by two percent a
year while the rest of the world population declined by one
percent a year.)
World population won't stop declining until
human values change. But human values may well change─values,
not biological imperatives, are the unfathomable variable
in population predictions. It is quite possible that in a
century or two or three, when just about the whole world is
at least as modern as Western Europe is today, people will
start to value children more highly than they do now in modern
societies. If
they do, and fertility rates start to climb, fertility is
no more likely to stop climbing at an average rate of 2.1
children per woman than it was to stop falling at 2.1 on the
way down.
In only the past twenty years or so world
fertility has dropped by 1.5 births per woman. Such a degree
of change, were it to occur again, would be enough to turn
a long-term increase in world population of one percent a
year into a long-term decrease of one percent a year. Presumably
fertility could someday increase just as quickly as it has
declined in recent decades, although such a rapid change will
be less likely once the world has completed the transition
to modernity. If fertility rises only to 2.8, just 33 percent
over the replacement rate, world population will eventually
grow by one percent a year again─doubling in seventy years
and multiplying by twenty in only three centuries.
The decline in fertility that began in some
countries, including the United States, in the past century
is taking a long time to reduce world population because when
it started, fertility was very much higher than replacement
level. In addition, because a preference for fewer children
is associated with modern societies, in which high living
standards make time valuable and children financially unproductive
and expensive to care for and educate, the trend toward lower
fertility couldn't spread throughout the world until economic
development had spread. But once the whole world has become
modern, with fertility everywhere in the neighborhood of replacement
level, new social values might spread worldwide in a few decades.
Fashions in families might keep changing, so that world fertility
bounced above and below replacement rate. If each bounce took
only a few decades or generations, world population would
stay within a reasonable narrow range─although probably
with a long-term trend in one direction or the other.
The values that influence decisions about
having children seem, however, to change slowly and to be
very widespread. If the average fertility rate were to take
a long time to move from well below to well above replacement
rate and back again, trends in world population could go a
long way before they reversed themselves. The result would
be big swings in world population─perhaps down to one or
two billion and then up to 20 to 40 billion.
Whether population swings are short and narrow
or long and wide, the average level of world population after
several cycles will probably have either an upward or a downward
trend overall. Just as averaging across the globe need not
result in exactly 2.1 children per woman, averaging across
the centuries need not result in zero growth rather than a
slowly increasing or slowly decreasing world population. But
the long-term trend is less important than the effects of
the . The troughs could be so low that
human beings become fewer than they were in ancient times.
The peaks might cause harm from some kinds of shortages.
One implication is that not even very large
losses from disease or war can affect the world population
in the long run nearly as much as changes in human values
do. What we have learned from the dramatic changes of the
past few centuries is that regardless of the size of the world
population at any time, people's personal decisions about
how many children they want can make the world population
go anywhere─to zero or to 100 billion or more.
(1 916 words)
(From The Atlantic Monthly, Vol, 284,No.
2 Aug 1999)
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