Transcript Why Is Population Increasing at Different Rates?

Why Is Population Increasing at Different
Rates?
A country’s stage of demographic
transition gives it a distinctive
population structure.
Population in a country is influenced by
the demographic transition in two
important ways:
% of pop in each age group
Distribution of males and females
Why Is Population Increasing at Different
Rates?
Population pyramids-p.62-63
A bar graph showing a place’s age and sex
composition
Shape of the pyramid is determined mainly
by the CBR
Age distribution
Dependency ratio-# of people too young or too
old to work, compared to # of people in their
productive years.
Sex distribution
Sex ratio-# of males per 100 females in the pop.
Population
Pyramids
See p.64
Figure 2-16
Percent of Population under 15
Fig. 2-15: About one-third of world population is under 15, but the percentage by country
varies from over 40% in most of Africa and some Asian countries, to under 20%
in much of Europe.
Why Is Population Increasing at Different
Rates?
Countries are in different stages of the
demographic transition
Three examples:
Cape Verde = High growth
Stage 2 since the 1950s
Chile = Moderate growth
Stage 3 since the 1960s
Denmark = Low growth
Stage 4 since the 1970s
Rapid Growth in Cape Verde
Fig. 2-17: Cape Verde, which entered stage 2 of the demographic transition in about
1950, is experiencing rapid population growth. Its population history
reflects the impacts of famines and out-migration.
Moderate Growth in Chile
Fig. 2-18: Chile entered stage 2 of the demographic transition in the 1930s, and it
entered stage 3 in the 1960s.
Low Growth in Denmark
Fig. 2-19: Denmark has been in stage 4 of the demographic
transition since the 1970s, with little population
growth since then. Its population pyramid shows
increasing numbers of elderly and few children.
Why Is Population Increasing at Different
Rates?
Demographic transition & world
population growth
Most countries = stage 2 or stage 3 of
the Demographic Transition
Stages 2 and 3 are characterized by
significant population growth
No country is in stage 1 of the
demographic transition
It is easier to cause a drop in the CDR
than in the CBR
Key Issue 4
Why Might the World Face an Overpopulation
Problem?
Why Might Overpopulation be a
Concern?
 Thomas Malthus on overpopulation:
 One of the first to argue that the world’s rate of
population increase was far outrunning the
development of food supplies.
 An Essay on the Principle of Population (1798):
Population grows geometrically while food supply
grows arithmetically
Why Might Overpopulation be a
Concern?
 Neo-Malthusians:
 Argue that 2 characteristics of recent population growth make Malthus’s
thesis even more scary than it was 200 years ago:
 Malthus failed to predict that LDCs would have the most rapid pop
growth because of medical technology not wealth
 World pop is not only exceeding food production, but other resources,
like clean air, suitable farmland, and fuel
Why Might Overpopulation be a
Concern?
 Criticism of Malthus includes the following:
Pessimistic viewpoint
 Ideas based on a belief that the world’s supply of resources is
fixed rather than expanding.
 Failure to consider technological innovation
 Larger pop could stimulate economic growth
Marxist critique
 Argue that issues like poverty, hunger, and social welfare
problems are due to unjust social and economic institutions, not
pop growth
Malthus: Theory & Reality
Figure 2-25
Food and Population, 1950–2000
Malthus vs. Actual Trends
Fig. 2-20: Malthus predicted population would grow faster than
food production, but food production actually
expanded faster than population in the second half of
Why Might Overpopulation be a
Concern?
 The NIR only declines for 2 reasons: lower CBR or
higher CDR.
 Declining birth rates
 Reasons for declining birth rates:
Reliance on economic development
 Improving local economic conditions, including
education and health care
Distribution of contraceptives
Reducing birth rates with contraception
Opposition for religious and political reasons
Crude Birth Rate Decline, 1981–
2001
Fig. 2-21: Crude birth rates declined in most countries between 1981
and 2001 (though the absolute number of births per year
increased from 123 to 133 million).
Family Planning
Figure 2-22
Why Might Overpopulation be a
Concern?
 World health threats
The epidemiologic transition
Stage 1: Pestilence and famine
The Black Plague
Pandemics
Why Might Overpopulation be a
Concern?
 World health threats
The epidemiologic transition
Stage 2: Receding pandemics
Cholera and Dr. John Snow
Cholera in London, 1854
Fig. 2-23: By mapping the distribution of cholera cases and water
pumps in Soho, London, Dr. John Snow identified the source
of the waterborne epidemic.
Why Might Overpopulation be a
Concern?
 World health threats
The epidemiologic transition
Stage 3: Degenerative diseases
Most significant: Heart disease and
cancer
Stage 4: Delayed degenerative diseases
Medical advances prolong life
Why Might Overpopulation be a
Concern?
 World health threats
 The epidemiologic transition
A possible stage 5: Reemergence of infectious
diseases?
Three reasons why it might be happening:
Evolution of disease
Poverty
Improved travel
Tuberculosis Death Rates, 2000
Fig. 2-24: The tuberculosis death rate is a good indicator of a
country’s ability to invest in health care. TB is still one of the
world’s largest infectious-disease killers.
SARS Infections in China, 2003
Fig. 2-25: China had 85 percent of the world's SARS cases in 2003. Within
China, the infection was highly clustered in Guangdong Province,
Hong Kong, and Beijing.
HIV/AIDS Prevalence Rates, 2002
Fig. 2-26: The highest HIV infection rates are in sub-Saharan Africa.
India and China have large numbers of cases, but lower
infection rates at present.