Learning Outcomes After studying this chapter, you should be able to answer the following questions:
• Why are we concerned about human population growth?
• Will the world’s population double again as it did between 1965 and 2000?
• What is the relationship between population growth and environmental impact?
• Why has the human population grown so rapidly since 1800?
• How is human population growth changing in different parts of the world?
• How does population growth change as a society develops?
• What factors slow down or speed up human population growth?
For every complex problem there is an answer that is clear, simple, and wrong. –H. L. Mencken 4-
4.1 Past and Current Population Growth Are Very Different
Every second, on average, four or five children are born, somewhere on the earth. In that same second, two other people die.
The U.S. Census Bureau estimates the mid-2008 world population to be about 6.7 billion people and growing at 1.15 percent per year.
Human populations grew slowly until recently 4-
Human populations throughout history 4-
4.2 Perspectives on Population Growth
Does environment or culture control human population growth?
Technology increases carrying capacity for human beings.
Population growth could bring benefits, such as economic growth.
4.3 Many Factors Determine Population Growth
Demography encompasses vital statistics about people, such as births, deaths, and where they live, as well as total population size.
Fecundity is the physical ability to reproduce, while fertility is the actual production of offspring.
The total fertility rate is the number of children born to an average woman in a population during her entire reproductive life.
Zero population growth (ZPG) occurs when births plus immigration in a population just equal deaths plus emigration.
4.3 Many Factors Determine Population Growth continued…
Factors affecting population growth
Fertility varies among cultures and at different times
Mortality offsets births
Life expectancy is rising worldwide
Living longer has profound social implications
Fertility varies among cultures and at different times
Fertility rates have declined dramatically in every region of the world except Africa over the past 50 years.
Life span is the oldest age to which a species is known to survive.
Life expectancy is the average age that a newborn infant can expect to attain in any given society.
Age class histograms 4-
People want children for many reasons
Factors that increase people’s desires to have babies are called pronatalist pressures.
Children may be the only source of support for elderly parents in countries without a social security system.
Often children are valuable to the family not only for future income but even more as a source of current income and help with household chores .
Society also has a need to replace members who die or become incapacitated.
Education and income affect the desire for children
Highly developed countries.
Higher education and personal freedom affect women to not have children.
The desire to spend time and money on other priorities limits the number of children.
Feeding and clothing is minimally expensive, adding one more child is negligible.
4.5 A Demographic Transition Can Lead to Stable Population Size
Demographic transition is a typical pattern of falling death rates and birth rates due to improved living conditions that usually accompanies economic development.
Economic and social conditions change mortality and births
Stage I in figure 4.13 represents the conditions in a premodern society.
Economic development in Stage II brings better jobs, medical care, sanitation, and a generally improved standard of living, and death rates often fall very rapidly.
Note that populations grow rapidly during Stage III when death rates have already fallen but birth rates remain high.
Stage IV represents conditions in developed countries, where the transition is complete and both birth rates and death rates are low, often a third or less than those in the predevelopment era.
The following factors help stabilize populations:
Growing prosperity and social reforms that accompany development reduce the need and desire for large families in most countries.
Technology is available to bring advances to the developing world much more rapidly than was the case a century ago.
Less-developed countries have historic patterns to follow.
Modern communications (especially television) have caused a revolution of rising expectations that act as stimuli to spur change and development.
Two ways to complete the demographic transition
The Indian states of Kerala and Andra Pradesh exemplify two approaches to population growth.
Social justice strategy: In Kerala, providing a fair share of social benefits to everyone was the key to completing the demographic transition.
Birth control strategy: Andra Pradesh adopted a strategy of aggressively promoting birth control, rather than social justice
Improving women’s lives helps reduce birth rates
A broad consensus reached by the 180 participating countries agreed that :
responsible economic development,
education and empowerment of women, and
high-quality health care (including family planning services) must be accessible to everyone if population growth is to be slowed.
Total fertility declines as women’s education increases 4-
4.6 Family Planning Gives Us Choices
Family planning allows couples to determine the number and spacing of their children.
Birth control usually means any method used to reduce births.
The major categories of birth control techniques
(1) avoidance of sex during fertile periods (for example, celibacy or the use of changes in body temperature or cervical mucus to judge when ovulation will occur)
(2) mechanical barriers that prevent contact between sperm and egg (for example, condoms, spermicides, diaphragms, cervical caps, and vaginal sponges)
(3) surgical methods that prevent release of sperm or egg (for example, tubal ligations in females and vasectomies in males)
(4) hormone-like chemicals that prevent maturation or release of sperm or eggs or that prevent embryo implantation in the uterus (for example, estrogen plus progesterone, or progesterone alone, for females; gossypol for males)
(5) physical barriers to implantation (for example, intrauterine devices)
4.7 What Kind of Future Are We Creating Now?
Most demographers believe that world population will stabilize sometime during the twenty-first century.
When we reach that equilibrium, the total number of humans is likely to be somewhere around 8 to 10 billion.
1. About how many years of human existence passed before the world population reached its first billion? What factors restricted population before that time, and what factors contributed to growth after that point?
2. Describe the pattern of human population growth over the past 200 years. What is the shape of the growth curve (recall chapter 3)?
3. Define ecological footprint. Why is it helpful, but why might it also be inaccurate?
4. Why do some economists consider human resources more important than natural resources in determining a country’s future?
Practice Quiz continued…
5. In which regions of the world will most population growth occur during the twenty-first century? What conditions contribute to rapid population growth in these locations?
6. Define crude birth rate, total fertility rate, crude death rate, and zero population growth.
7. What is the difference between life expectancy and life span? Why are they different?
8. What is the dependency ratio, and how might it affect the United States in the future?
9. What factors increase or decrease people’s desire to have babies?
10. Describe the conditions that lead to a demographic transition.