Page 571 - Sociology and You

Chapter 16 Population and Urbanization
half of the twenty-first century, the annual growth rate is ex- pected to decline until world population stabilizes at about eleven billion people. (See Figure 16.5.) At this point, the world will have reached zero population growth—when deaths are balanced by births so that the population does not in- crease (World Population Data Sheet, 2001).
Contrary to popular belief, limiting the average family size to two children does not imme- diately produce zero population growth. There is a time lag of sixty to seventy years because of the high proportion of young women of childbearing age in the world’s population. Even if each of these women had only two children, the world popula- tion would grow.
The time lag is what demog-
raphers call population momentum. The growth of the world’s population, like a huge boulder rolling down a mountain, cannot be stopped immedi- ately. But the sooner the momentum of current population growth is halted, the better. The sooner the world fertility rate reaches the replacement level (the rate at which people replace themselves without adding to the popula- tion) the sooner zero population growth will be reached. The ultimate size of the world’s population, when it does stop growing, depends greatly on the timing of reaching replacement level. To state it another way, for each decade it takes to reach replacement level, the world’s population will in- crease by 15 percent.
Population Control
As discussed earlier, death rates in both developing and developed na- tions have already dropped dramatically. Any significant progress in curbing world population growth must concentrate on lowering birth rates. Population control refers to the conscious attempt to regulate population size through national birth control programs.
Is government-sponsored population control new? Historically, most societies were more concerned with increasing the population than with overpopulation. Many births were needed to offset the high death rates from disease and poor hygiene. With surplus populations, aggressive nations were able to maintain larger armies. Agricultural societies needed large num- bers of people to work the land. Aging parents wanted to be more secure in old age. High birth rates were also encouraged in countries with religious laws against birth control.
541
Three Possible Futures
30 25 20 15 10
5
0
1950 1970 1990 2010 2030 2050 2070 2090 2110 2130 2150
Year
High Scenario
(2.6 children per woman)
Medium Scenario
(2.0 children per woman)
Low Scenario
(1.6 children per woman)
Figure 16.5 Long-Range Projections of World Population: 2000–2150.
The United Nations’ estimate of future growth is based on three different assumptions. The high scenario would push world population growth to over 27 billion. The medium scenario would result in a world population of about 11 billion. The low scenario would leave the world population at about 4 billion.
Source: Population Reference Bureau, Washington, DC, 2001.
zero population growth
situation in which deaths are balanced by births so that the population does not increase
population momentum
inability to stop population growth immediately because of previous high rate of growth
replacement level
birth rate at which a couple replaces itself without adding to the population
population control
attempts by government to control birth rates
Billions of persons