Our numbers expand, but Earth’s
natural systems do not
Lester R. Brown
Human Populations
Unit 9
Studying Human Populations
• Demography: study of the
characteristics of human
populations.
• -size and makeup of the
populations.
• -properties that affect
population growth- economics
and social structure.
Demographics
• Countries are grouped into two categories:
developed and developing countries.
• Developed countries have:
-higher average incomes
-slower population growth
-diverse industrial economies
-access to education
Demographics (cont’d)
Developing countries have:
– lower average incomes
– rapid population growth.
– simple and agriculture-based economics
– limited access to education
The Human Population Over Time
• Exponential growth began in the 1800s.
• -due to increases in food production and
improvements in hygiene that came with the
industrial/scientific revolution.
• FYI: It is unlikely that the Earth can sustain this
growth for much longer
World Population Over Time
Age Structure
• Age structure: the classification of a population
according to reproductive age.
• -countries with more young people have high
growth rates
• -countries with an even distribution of ages have
slow or no growth
Age Structure
• Population pyramid: double-sided bar graph
showing age structure.
Survivorship
• Survivorship: the percentage of newborns
expected to survive to a given age.
• -used to predict population trends
• -to predict survivorship, demographers study a
group of people born at the same time and notes
when each member of the group dies.
Survivorship Curve
• The results of these
studies are then
plotted on a graph
and might look like
one of the types of
survivorship graphs.
Survivorship
• Survivorship curves:
• Type I: most people live to be very old. ex. Japan,
Germany
• Type II: population members have a similar death
rate at all ages.
• Type III: many children die. ex. India, subsaharan
Africa
• -Both Type I and Type III may result in populations
that remain the same size or grow slowly.
Fertility Rates
• Fertility rate: number of births per
1,000 women of childbearing age
(usually 15 to 44).
• Replacement level: average
number of children each parent
must have in order to “replace”
themselves.
• -number is slightly more than 2
because not all children born will
survive and reproduce.
Fertility Rates
• 1972: total fertility dropped below
replacement level for the first time in US
history.
• Fertility rates remained below replacement
level for most of the 1990s, but recently has
been growing partly because the children of
the baby boom grew up and had children.
Fertility Rates
Migration
• Migration: any movement of
individuals from one location
to another.
• -immigration: movement
into an area.
• -emigration: movement out
of an area.
Declining Death Rates
• The dramatic increase in Earth’s human
population in the last 200 years has happened
because death rates have declined more rapidly
than birth rates.
• Death rates have declined because more people
have access to:
-adequate food
-clean water
-safe sewage disposal
-vaccines
Life Expectancy
• Life expectancy: average length
of time that an individual is
expected to live.
• -most affected by infant
mortality, the death rate of
infants less than a year old.
• -infant health is most affected by
the parents’ access to education,
food, fuel, and clean water.
Life Expectancy
• The graph shows that
average life expectancy
worldwide has
increased to more
than 67 years old. But,
new threats, such as
tuberculosis and AIDS
are arising as
populations become
denser.
The Demographic Transition
• Demographic transition: general pattern of
demographic change from high birth and
death rates to low birth and death rate.
• -the theory behind the demographic transition
is that industrial development causes
economic and social progress which affects
population growth rates.
Stages of the Transition
1. Preindustrial stage:
-high birth and death rates; population size is
stable.
2. Transitional:
-population explosion occurs.
-death rates decline as hygiene, nutrition, and
education improve.
-birth rates remain high, so population grows
fast.
Stages of the Transition
3. Industrial:
-population growth slows as birth rate
decreases.
-birth rate becomes close to the death rate; the
population size stabilizes.
4. Postindustrial:
-birth rate drops below replacement level;
population begins to decrease.
Women and Fertility
• Factors most clearly related to a decline in
birth rates:
• -increasing education and economic
independence for women.
• (educated women find that they do not need
to bear as many children to ensure that some
will survive. They may also learn family
planning techniques.)
So…
1.
2.
3.
4.
5.
6.
What is demography?
What does an age structure graph show?
What is survivorship?
What are the three types of survivorship curves?
What is fertility rate?
What is the difference between emigration and
immigration?
7. What are the four stages to demographic
transition?
U.S. Population Growth
• 1.66 million more births than deaths
• 800,000- 1,000,000 legal immigrants
-53% from Latin America
-25% from Asia
-14% from Europe
 300,000 illegal immigrants (est 11 million)
 Projected growth by 2050: 41% to 86%
(Pacific NW growth is higher than India!)
Reasons for Projected U.S. Growth
• Large numbers of baby boom woman still in
child-bearing years
• Increase in number of unmarried mothers
 High levels of immigrants
 Inadequate family-planning services
Demographic Data Project
• Choose a partner or you may work alone.
• Choose a country that interests you (maybe
country of origin of your ancestors).
• Create a ppt presentation with the following
data…
Demographic Data
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•
•
•
•
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Name of country
Area in km; location on global (include a map)
Number of people; population per square m
Birth rate (per 1000) and death rate (per 1000)
Projected population in 2025 (millions)
Infant mortality
Total fertility rate
Life expectancy at birth for males; for females
Presentations
• Only use bulleted points, not whole sentences
• Use font size 28-32 for body (titles can be 3644)
• Must include the following visuals: map,
people, land
• Email your ppt to ann.erbele@sccpss.com
Web Resources:
Population Reference Bureau
United Nations