Environmental Engineering Reference
In-Depth Information
Before going on, a word about population is in order.
Income and population taken together give a measure of
the standard of living, the per capita GDP. Much of the
drive for rapid economic growth comes from pressures to
increase the standard of living of a country
'
s population.
The world population was about
.
billion in
;it
doubled to
billion by
; it doubled again to
billion
by
. This booming population required an associated
boom in energy use to maintain the world average stand-
ard of living, and an even larger boom to improve it. If the
time for the population to double continued to shrink, the
world would be in even more serious trouble than it is
today, but, fortunately, population growth is slowing.
Population can be predicted with reasonable accuracy
for the next
years and with lesser accuracy for the
rest of the century. Almost every woman who will have a
child in the next
to
years has already been born. We know
current fertility factors (children per female) and we can
project fertility with con
dence for several decades. The
longer-term projection is where the major uncertainty
lies. Fertility has been declining all over the world, and
each new long-term prediction implies it will decline
faster than assumed in the last prediction. It seems almost
universal that as income goes up, fertility goes down.
Some ascribe this to the move to the cities where fewer
children are needed to support the family. Others say that
it is simply that as women have more opportunity they
have fewer children. Whatever the reason, predictions for
future population have been coming down. Population
trends for the world are analyzed by the United Nations
Population Division (
www.un.org/esa/population/unpop.
