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Chapter 11
Human Population:
Growth & Distribution
© Brooks/Cole Publishing Company / ITP
Outline
1. Factors Affecting Human Population Size
birth & death rates
2. Population Age Structure
age structure diagrams, developing vs. developed countries
3. Solutions: Stabilizing Human Population
computer models, demographic transition
4. Case Studies
United States, India, China
5. Human Population & Sustainability
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Human Population Growth
How would you describe the population before 1700?
Human Population Growth
How would you describe the population after 1700?
Human Population Growth
What kinds of historical events were taking place in the 1700s
and 1800s?
Human Population Growth
How has the amount of time it takes for the population to
grow by 1 billion changed?
Human Population Growth
Population Year Reached Years to Reach
1 billion
1850
Tens of thousands
2 billion
1930
80
3 billion
1960
30
4 billion
1974
14
5 billion
1987
13
6 billion
2000
12
Factors Affecting Human Population Size
Human population is
currently growing
exponentially:
• What will be the
ultimate size of the
human population?
• What is Earth's
carrying capacity?
(How many humans
can Earth support?)
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Factors Affecting Human Population Size
Population change is calculated as the difference
between individuals entering and leaving a population:
Population Change
=
Births
+
Immigration
–
Deaths
+
Emigration
• Birth rate – is the number of births per thousand people
• Death rate – is the number of deaths per thousand
people
• Zero population growth (ZPG) occurs when factors
that increase and decrease population size balance
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Crude Birth & Death Rates
Developed
countries tend to
have lower birth
rates & death rates
than developing
countries.
Why?
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Population Change
The annual rate of
population
increase is
generally
expressed as a
percentage.
What information
can you gather
from this map?
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Population Size by Continent
Population size by
region in 1998,
with projections of
population size in
2025.
There are about
84 million births
each year.
(97% of new births
are in developing
countries)
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Population Size
Fertility Rates
Measure of the number of children that will be born
1) Replacement Fertility - Number of children needed
to replace the parents (2.1 in developed countries,
2.5 in some developing countries)
2) Total Fertility Rate (TFR) - Average number of
children each woman has in a population from 15 - 45
Average TFR (births per woman)
2.8 - Developing Countries
2.4 - Middle Income Countries
1.7 - Upper Income Countries
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Total Fertility in the United States
Total fertility in the United States had a major increase
during the "baby boom" (1946–1964) & is now hovering
just below replacement level.
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Factors Affecting Fertility Rates
What factors decrease human fertility levels?
What causes people to have fewer children?
How do you
get a baby
astronaut to
fall asleep?
You rocket.
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Factors Affecting Fertility Rates
The following are significant factors that decrease
human fertility levels:
•
•
•
•
•
•
•
•
•
•
•
increase in average level of education & affluence
decrease in importance of child labor
increased urbanization
increased cost of raising & educating children
increased educational & employment opportunities for women
decreased infant mortality
higher average age of marriage
greater availability of private & public pensions
greater availability of reliable birth control
greater availability of legal abortions
change in religious beliefs, traditions, & cultural norms away
from encouraging large families
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TFR (Births per Woman)
Birth Control
Typical
effectiveness of
birth control
methods in the
United States:
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Birth Control
Typical
effectiveness of
birth control
methods in the
United States
(continued):
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Indicators of Health
“It’s not as if people suddenly started
breeding like rabbits; it’s just that they
stopped dying like flies.” Peter Adamson
Life expectancy - The number of years a
newborn can expect to live
Developing Countries - 64.6 years
Middle Income Countries - 69.6 years
Upper income Countries - 78.2 years
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Indicators of Health
“It’s not as if people suddenly started
breeding like rabbits; it’s just that they
stopped dying like flies.” Peter Adamson
Infant mortality - Number of babies out of
every 1,000 that die within a year of birth
Angola – 182.3
India – 32.3
United States – 6.3
Singapore – 2.3
World Average – 42.1
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Death Rates
Infant death
rates are lower
in developed
countries than
developing
countries
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Infant Mortality Rate vs. GDP
Birth & Death Rates Over Time
The rapid growth in the world's population has not
resulted from an increase in birth rates, but rather a
major decrease in death rates.
• death rates have decreased markedly during the past
100 years
• birth rates have also decreased, but not as fast as
death rates
• the increasing difference between birth & death rates
is what has lead to exponential population growth
• the patterns of change in birth & death rates over time
are different for developed vs. developing countries
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Birth & Death Rates Over Time
In developed
countries,
decreases in
death rates
are being
accompanied
by decreases
in birth rates
over time.
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Birth & Death Rates Over Time
In developing
countries,
decreases in
death rates have
not been
accompanied by
as large of
decreases in
birth rates over
time, leading to
major population
increase.
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Teen Pregnancy
• Which industrialized country has the
highest teenage pregnancy rate?
The United States
• How many teenage girls become
pregnant each year?
872,000
• What percentage of those pregnancies
were unplanned?
78%
Think About It
•
Which age group do you think has the
biggest population in Chester County?
Chester County, PA
Population Age Structure
Age structure refers to the proportion of the
population in each age class:
• prereproductive (0–14 years)
• reproductive (15–44 years)
• postreproductive (45 & up)
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Population Age Structure
Age structure of a rapidly growing vs. a slower growing population.
Rapidly growing
populations have
pyramid–shaped
age structures,
with large numbers
of prereproductive
individuals. Slower
growing
populations have a
more even age
distribution.
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Population Age Structure
Age structure of populations with zero growth vs. negative growth.
Populations with
zero population
growth have nearly
equal proportions
of prereproductive
& reproductive
individuals;
whereas
populations with
negative growth
have a greater
proportion of
reproductive than
prereproductive
individuals.
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Matching Review
B
C
A. Rapid Growth
B. Zero Growth
A
D
C. Negative Growth
D. Slow Growth
Population Age Structure
Population age structure of the United States continues
to show a bulge as the “baby boom” generation ages.
This has been compared to watching a boa constrictor
swallow a pig.
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Demographic
Indicators
Fig.11–15
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Population Age Structure
Developing
countries are
expected to
continue to have
a pyramid shape
through the year
2025, although
the age structure
will become
somewhat more
evenly
distributed.
Fig.11–14a
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Population Age Structure
Populations of
developed
countries are
expected to have an
increasingly even age
distribution through
the year 2025.
Fig.11–14b
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Developed vs. Developing
Demographic Transition
A generalized model of demographic transition
Demographic Transition
1) Preindustrial Stage:
•
Birth rate and death rates
are high & approximately
equal
•
population does not
increase
•
population size is small
Death rate
Birth rate
Total pop.
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Demographic Transition
2) Transitional Stage:
• death rate decreases
because of
industrialization,
increased food
production, & improved
health care
• birth rate remain high
• population grows rapidly
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Demographic Transition
3) Industrial Stage:
•
birth rate drops & eventually
approaches a balance with
death rate
Total pop.
• slowing of population growth
Birth rate
Death rate
Demographic Transition
4) Postindustrial Stage:
•
birth rate & death rates
approximately balance
•
zero population growth
•
population stabilizes at a size
much higher than the
preindustrial size
•
if birth rate declines below death
rate negative population growth
may even be attained
Total pop.
Death rate
Birth rate
Computer Models of Human Population
This computer model projects what might happen if
the world's population & economy continue to grow
exponentially at 1990 levels.
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Computer Models of Human Population
This computer model projects how we can avoid
overshoot & collapse to make a fairly smooth
transition to a sustainable future by stabilizing fertility
at two children per couple.
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Case Studies – Population
Control in India
• In 1952, India began the first
national family planning
program
• The program has been
disappointing because of poor
planning, low status of women,
extreme poverty, & lack of funds
• Couples still have an average of
3.5 children because of the
belief that they need children to
work & care for them in old age
India
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Case Studies – Population
Control in China
• Since 1970, China has
initiated efforts to better feed
its people & control
population growth
• Strict population control
measures prevent couples
from having more than one
child
• Although considered
coercive, the policy is
significantly slowing
population growth
China
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Case Studies – Immigration in
the U.S.
• As fertility decreases,
immigration has
become a major
source of population
increase in the U.S.
• In 1998, the U.S.
received about
935,000 legal
immigrants & 400,00
illegal immigrants
• Increasing levels of
legal & illegal
immigrants are
expected
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Immigration
in the
U.S.A.!
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Immigration in the United States
Should the U.S. reduce the number of
immigrants allowed into the country?
Is the U.S. (or other wealthy countries)
obligated to accept immigrants from
very poor countries?
Human Population & Sustainability
How can governments reduce population growth?
• improve access to family planning & reproductive health care
• improve heath care for infants, children, & pregnant women
• encourage development of national population policies
• improve equality between men & women
• increase access to education, especially for girls
• increase the involvement of men in child rearing & family
planning
• reduce poverty
• reduce & eliminate unsustainable patterns of production &
consumption
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