Demographic Transition and Age Structure

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Demographic Transition and Age Structure
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Variations in Population Growth

• The Demographic Transition
• 1. Low growth 3. Moderate growth
• 2. High growth 4. Low growth
• Population pyramids
• Age distribution
• Sex ratio
• Countries in different stages of demographic
  transition
• Demographic transition and world population growth

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Earths Population History
6 billion reached 1999 (12 years later)
5 billion reached 1987 (13 years later)
4 billion reached 1974 (15 years later)
3 billion reached 1959 (29 years later)
2 billion reached 1930 (100 years later)
1 billion reached circa 1830
Source Kuby, HGIA
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World Population Growth Rates, 400,000 BC - AD
2000
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Demographic Transition Model Explaining Spatial
Patterns of World Population Growth
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The Demographic Transition
Fig. 2-13 The demographic transition consists
of four stages, which move from high birth and
death rates, to declines first in death rates
then in birth rates, and finally to a stage of
low birth and death rates. Population growth is
most rapid in the second stage.
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Demographic Transition Model
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Stages in Classic 4-Stage Demographic Transition
Model (DTM) (Some books show a 3-stage model
others mention a new 5th stage)
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Stage 1 Pre-Industrial High birth rates and
high death rates (both about 40) Population
growth very slow Agrarian society High rates of
communicable diseases Pop. increases in good
growing years declines in bad years (famine,
diseases) No country or world region still in
Stage One
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Stage 2 Early Industrial High birth rates
(over 30) but death rates decline (to about
20) RNIs increase sharply (pop. explosion)
growth rate increases throughout Stage
Two Growth not from increase in births, but from
decline in deaths MDCs starts early 1800s LDCs
starts after 1950s
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TRANSITION TO STAGE TWO IN CLASSIC DTM Known as
the Epidemiologic Transition Agricultural
technology Improvements in food supply higher
yields as agricultural practices improved in
Second Agricultural Revolution (18th
century) In Europe, food quality improved as
new foods introduced from Americas Medical
technology Better medical understanding (causes
of diseases how they spread) Public sanitation
technologies Improved water supply (safe
drinking water) Better sewage treatment, food
handling, and general personal hygiene Improveme
nts in public health especially reduced childhood
mortality
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Declining Infant Mortality Rates
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Stage 3 Later Industrial Birth rates decline
sharply (to about 15) Death rates decline a bit
more (to about 10 or less) Note growth still
occurs, but at a reduced and declining rate MDCs
starts in late 1800s LDCs starts after
1980s Or hasnt started yet
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Stage Three Further improvements in medicine
lower death rates more raise life expectancies
Measles Mortality, US, since 1900
TB Mortality, US, since 1900
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TRANSITION TO STAGE THREE IN CLASSIC DTM Known as
the Fertility Transition Societies become more
urban, less rural Declining childhood death in
rural areas (fewer kids needed) Increasing
urbanization changes traditional values about
having children City living raises cost of
having dependents Women more influential in
childbearing decisions Increasing female
literacy changes value placed on motherhood as
sole measure of womens status Women enter work
force life extends beyond family, changes
attitude toward childbearing Improved
contraceptive technology, availability of birth
control But contraceptives not widely avail in
19th century contributed little to fertility
decline in Europe Fertility decline relates
more to change in values than to availability
of any specific technology
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Population Classified as Urban
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Strong inverse relationship between female
literacy and fertility rates, observed globally
Increasing availability and use of modern
contraception in most LDCs since 1970s
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Stage 4 Post-Industrial Birth rates and
death rates both low (about 10) Population
growth very low or zero MDCs starts after
1970s LDCs hasnt started yet Stage 5 (?)
Hypothesized (not in Classic DTM) Much of Europe
now or soon in population decline as birth rates
drop far below replacement level
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Demographic Transition in England
Fig. 2-14 England was one of the first
countries to experience rapid population growth
in the mid-eighteenth century, when it entered
stage 2 of the demographic transition.
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Key Population Indicators for Selected Countries
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Differences in DTM experience MDCs LDCs
? Faster decline in death rates Tech
improvements diffused from MDCs applied rapidly
in LDCs post-WW2 ? Longer lag between decline in
deaths and decline in births Stage 3 slower
start in LDCs where econ growth is delayed ?
Higher max rates of growth in LDCs Over 3.5
peak RNI in Mauritius and Mexico only 1.3 peak
in Sweden
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Age structures today in LDCs are much younger
than MDCs experienced leading to prolonged
Demographic Momentum expected growth of pop.
long after fertility declines
Percentage of Population Under Age 15
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Summary of DTM for LDCs Industrializing LDCs
with some economic development follow DTM more
closely now in Stage Three. Most like MDCs in
places where female literacy has increased the
most. Lowest-income countries have high birth
rates and deaths are leveling off at higher rates
than DTM predicts (Stage Two). In some LDCs,
death rates starting to increase (epidemics,
worsening poverty)
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AZ Breakdown by Ethnic Population Groups within
MDCs may have varying pop patterns
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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.
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Elderly Shoppers in Russia
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JAPAN
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Population Pyramids in U.S. cities
Fig. 2-16 Population pyramids can vary greatly
with different fertility rates (Laredo vs.
Honolulu), or among military bases (Unalaska),
college towns (Lawrence), and retirement
communities (Naples).
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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.
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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.
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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.
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Census taking in China
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Will the World Face an Overpopulation Problem?

• Malthus on overpopulation
• Population growth food supply
• Malthus critics
• Declining birth rates
• Malthus theory reality
• Reasons for declining birth rates
• World health threats
• Epidemiological transitions

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Fuel Wood Collection in Mali
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Food Population, 1950-2000Malthus 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 2nd half of the 20th century.
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Crude Birth Rate Decline, 1980-2005
Fig. 2-21 Crude birth rates declined in most
countries during the 1980s and 1990s (though the
absolute number of births per year increased from
about 120 to 130 million).
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Use of Family Planning
Fig. 2-22 Both the extent of family planning use
and the methods used vary widely by country and
culture.
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Women Using Family Planning
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Family Planning Methods used in three countries
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Promoting One-Child Policy in China
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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 water-borne
epidemic.
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Tuberculosis Death Rates
Fig. 2-24 The tuberculosis death rate is good
indicator of a countrys ability to invest in
health care. TB is still one of the worlds
largest infectious disease killers.
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Avian Flu, 2003 - 2006
Fig. 2-25 The first cases of avian flu in this
outbreak were reported in Southeast Asia.
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HIV/AIDS Prevalence Rates, 2005
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.
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The Spread of AIDS in Africa

•     20-30
•     10-20
•     5-10
•     1-5
•     0-1
•     data unavailable

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HIV-AIDS Weakens the Immune System

• Opportunistic infections
• Pneumonia
• Meningitis
• Some cancers
• Tuberculosis (TB)
• Other parasitic, viral and fungal infections that
  weaken the immune system

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Global Estimates HIV/AIDS

• People now living with HIV 40 million
• New HIV infections in 2005 4.9 million
• AIDS deaths up to 2005 25 million

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Growth of the AIDS Epidemic
People With HIV/AIDS, Cumulative Regional
Totals Millions
Western and Central Europe North
America. Source UNAIDS/WHO, 2004.
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Poverty and HIV-AIDS

• Inadequate access to accurate information or
  prevention services
• Seeing no alternative besides sex work, for some
  women
• Labor migration leads to increased
  vulnerability and spread of HIV
• Once infected, inadequate access to health care
  and treatment
• Vicious cycle of poverty, such as children
  orphaned because of AIDS

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AIDS Toll on Population Structure
Population Structure in South Africa
 2020 Millions
Age 80 75 70 65 60 55 50 45 40 35 30 25 20 15 10
5 0
Females
Males
Source United Nations, World Population
Prospects The 2004 Revision (CD-ROM
EditionExtended Dataset), 2005.
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Map of HIV Prevalence Worldwide
2005
Source UNAIDS, 2006 Report on the Global AIDS
Epidemic, 2006.
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Retired Man in Russia
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DTM only predicts changes in birth/death rates
over time Observed changes in RNI correlate to
changes in economic development Thus, DTM
implies The greater the wealth, the lower the
RNI ... but use caution describing this
relationship