Overpopulation.Com

The single most important factor
in determining future population is the total fertility rate (TFR). The
TFR is defined as the average number of babies born to women during their
reproductive years. A TFR of 2.1 is considered the replacement rate; once
a TFR of a population reaches 2.1 the population will remain stable assuming
no immigration or emigration takes place. When the TFR is greater than
2.1 a population will increase and when it is less than 2.1 a population
will eventually decrease, although due to the age structure of a population
it will take years before a low TFR is translated into lower population.

Although still high in many
parts of the world, total fertility rates have been declining dramatically
over the past decade. As the chart below illustrates, the world’s TFR
for 1998 was less than 3. In the more developed countries such as the
United States TFRs are already well below the replacement rate, though
in many of these countries population continues to grow due to the age
structure of the population as well as immigration. Currently 61
countries have a TFR of 2.1 or less.

The total fertility rate of
the less developed countries is twice as high as that of the more developed
countries, but it is falling — from 1985 to 1998 TFRs in the less developed
countries dropped almost 40 percent from 4.7 in 1986 to 3.2 in 1998. Although
the cause is debated, there is no doubt that women all over the world
are having fewer children.