6-2 What Factors Influence the Size of
the Human Population?
• Concept 6-2A Population size increases because of
births and immigration, and decreases through
deaths and emigration.
• Concept 6-2B The average number of children born
to women in a population (total fertility rate) is the
key factor that determines population size.
• The basics of global population change are quite
simple….
• If there are more births than the deaths during a
given time period….the population _______________
increases
• If there are less births than deaths….the population
______________
decreases
• If births and deaths are equal the population size
___________________
doesn’t change
The Human Population Can Grow,
Decline, or Remain Fairly Stable
• Instead of using total births or deaths, demographers use…
1000 people in a given
• Crude birth rate: # live births per ________
year
• Crude death rate: # deaths per __________
people in a given
1000
year
• Human population change depends on an interplay of three
factors…
• Births: _________________
fertility
• Deaths: _________________
mortality
• Migration
• Population change =
(births + immigration) – (deaths + emigration)
Women Having Fewer Babies but Not Few
Enough to Stabilize the World’s Population
• Fertility rate…number of children born to a woman
lifetime
during her ________________
• Replacement-level fertility rate…average number of
replace
children a couple must have to _______________
themselves
• 2.1 in developed countries
• Up to ________
in developing countries….because
2.5
some children _______
before reaching their
die
reproductive years
• Reaching replacement level-fertility rates does _____
NOT
immediately halt population growth….you have to
wait for ____________
girls to move through their
young
reproductive years
Women Having Fewer Babies but Not Few
Enough to Stabilize the World’s Population
• Total fertility rate (TFR)…Average number of
population
children born to women in a _________________
during their reproductive years
key
• TFR plays a _______
role in determining population
size
• World’s average TFR has dropped from 5 to 2.5
children, but needs to drop to _______
2.1
to halt world
population growth
Total fertility rate, 1955-2010
Which type
of country
has shown
the greatest
drop in TFR?
LDC
Fig. 6-5, p. 130
Total Fertility Rate
Figure 12, Supplement 8
Case Study: The U.S. Population Is
Growing Rapidly
• Our U.S. population has grown from _____
million in
76
310
1900 to ________
million in 2010
• Between 1946 and 1964 birth rates peaked
“baby boom”
• Called the _________________
• Added _______
79 million people to the U.S. population
• TFR was ______
3.7 children per woman
• Since 1972, TFR has been at or below _______
which
2.1
has _____________
our population growth (not as
slowed
1.5
low as China’s TFR _______)
Births per woman
4.0
3.5
3.0
2.5
2.1
2.0
1.5
1.0
0.5
Baby boom
(1946–64)
Replacement
level
0
Births per thousand population
1920
1930
1940
1950
1960
Year
1970
32
30
28
26
24
22
20
18
End of World War II
16 Demographic
Depression
Baby boom
Baby bust
14 transition
0
1920
1930
1940
1950
1960
1970
Year
1980
1990
2000
2010
Echo baby boom
1980
1990
2000
2010
Fig. 6-6, p. 131
• But our country’s growth rate is still _____________
higher
than many other more-developed countries
including China
• Changes in our U.S lifestyle during the 20th century
has also greatly increased our __________________
ecological
_________________
foootprint
2010 Rate of Population Increase
Figure 11, Supplement 8
47 years
Life expectancy
77 years
Married women working
outside the home
8%
81%
15%
High school
graduates
83%
10%
Homes with flush
toilets
Homes with
electricity
Living in
suburbs
Hourly manufacturing job
wage (adjusted for inflation)
Homicides per
100,000 people
98%
2%
99%
10%
52%
$3
1900
2000
$15
1.2
5.8
Stepped Art
Fig. 6-7, p. 132
• Since our ecological footprint is too large, many
demographers consider the U.S. to be
_____________________
overpopulated
Several Factors Affect Birth Rates and
Fertility Rates (1)
• Children as part of the ______________
labor
force
• ________
Cost of raising and educating children
pensions
• Availability of private and public ___________________
• Urbanization – better access to family _____________
planning
services
• Educational and employment opportunities for
women…better educated women tend to marry ___________
later
and have ____________
children
fewer
Several Factors Affect Birth Rates and
Fertility Rates (2)
first
• Average age of a woman at birth of _________
child
abortions
• Availability of legal _______________
• Each year about 190 million become pregnant and at
least ______
million women get abortions
40
birth-control
• Availability of reliable ________________
methods
Religious
• ______________
beliefs, traditions, and cultural
norms
Girl Carrying Well Water in India
In poorer
countries,
having more
children helps a
family to
complete their
tasks
daily _________
and survive
Fig. 6-8, p. 132
Child Laborers in India
Fig. 6-9, p. 133
Core Case Study
• In China, couples prefer to have a __________,
boy
because they are more likely to leave their family in
the future
• Some Chinese couples abort female fetuses…which
has lead to a __________
shortage
bride
Several Factors Affect Death Rates (1)
health
• Two factors indicate the overall __________
of a
population
• Life expectancy…average number of years of
newborn infant can be expected to live
• Infant mortality rate…number of live births that die in
first
_________
year
• Why are people living longer?
•
•
•
•
supply
Increased food _______________
and distribution
Better __________________
nutrition
medical
____________________
advances
sanitation
Improved ______________________
Several Factors Affect Death Rates (2)
• U.S. is 54th in world for infant mortality rate…
• somewhat high
_______ for a MDC
• U.S. infant mortality rate high due to
• Inadequate health care for ________
women during
poor
pregnancy and their infants
addictions
• Drug ________________
among pregnant women
teenagers
• High birth rate among ___________________
Infant Mortality Rates, 1950-2010
Fig. 6-10, p. 134
Migration Affects an Area’s Population
Size
• Migration – movement into (immigration) or out of
(emigration) a population
• Most migrating people are…
economic
• Seeking __________________
improvement
freedoms
• Seeking religious or political _______________
Escaping
• __________________
wars or environmental
problems (environmental __________________)
refugees
Case Study: The United States: A
Nation of Immigrants
• Currently, both legal and illegal immigration
36%
accounts for _________
of our annual population
growth
• Before 1960, most immigrants came from Europe
Latin-America and
• After 1960, most have __________________
_________________
Asia
• Controversy over immigration policy
60% of the American public supports reducing
• _______
legal immigration
• Reducing immigration will also affect our cultural
diversity
benefits
______________
and social security ______________
Legal Immigration to the U.S. between 1820 and 2006
Fig. 6-11, p. 135
Review Questions
• What has happened to the world’s TFR since 1950?
How has that affected our population growth?
Has decreased….slowed our growth
• Why is the infant mortality rate in the U.S. higher
than expected?
Inadequate health care for poor women
Drug addictions
High teenage pregnancy rates