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 _______________• If there are less births than deaths….the population

______________• If births and deaths are equal the population size

___________________

increases

decreases

doesn’t change

The Human Population Can Grow, Decline, or Remain Fairly Stable

• Instead of using total births or deaths, demographers use…

• Crude birth rate: # live births per ________ people in a given year

• Crude death rate: # deaths per __________ people in a given year

• Human population change depends on an interplay of three factors…• Births: _________________• Deaths: _________________• Migration

• Population change = (births + immigration) – (deaths + emigration)

1000

1000

fertilitymortality

Women Having Fewer Babies but Not Few Enough to Stabilize the World’s Population• Fertility rate…number of children born to a woman

during her ________________

• Replacement-level fertility rate…average number of children a couple must have to _______________ themselves• 2.1 in developed countries• Up to ________ in developing countries….because

some children _______ before reaching their reproductive years

lifetime

replace

2.5die

• Reaching replacement level-fertility rates does _____ immediately halt population growth….you have to wait for ____________ girls to move through their reproductive years

NOT

young

Women Having Fewer Babies but Not Few Enough to Stabilize the World’s Population• Total fertility rate (TFR)…Average number of

children born to women in a _________________ during their reproductive years

• 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 _______ to halt world population growth

population

key

2.1

Total fertility rate, 1955-2010

Fig. 6-5, p. 130

Which typeof countryhas shownthe greatestdrop in TFR?

LDC

Figure 12, Supplement 8

Total Fertility Rate

Case Study: The U.S. Population Is Growing Rapidly

• Our U.S. population has grown from _____ million in 1900 to ________ million in 2010

• Between 1946 and 1964 birth rates peaked• Called the _________________• Added _______ million people to the U.S. population• TFR was ______ children per woman

• Since 1972, TFR has been at or below _______ which has _____________ our population growth (not as low as China’s TFR _______)

76310

“baby boom”

793.7

2.1slowed

1.5

Fig. 6-6, p. 131

4.03.5

2.5

Baby boom (1946–64)

Replacement level

Bir

ths

per

wo

man

0.5

01920 1930 1940 1950 1960 1970 1980 1990 2000 2010

Year

32 30 28 26 24 22 20 18 16 14

0

transition Depression Baby boom Baby bust Echo baby boomDemographic End of World War II

Bir

ths

per

th

ou

san

d p

op

ula

tio

n

1920 1930 1940 1950 1960 1970 1980 1990 2000 2010Year

2.12.0

1.01.5

3.0

• But our country’s growth rate is still _____________ than many other more-developed countries including China

• Changes in our U.S lifestyle during the 20th century has also greatly increased our __________________ _________________

higher

ecologicalfoootprint

2010 Rate of Population Increase

Figure 11, Supplement 8

77 yearsLife expectancy 47 years

1900

2000

Married women working outside the home

8%81%

High school graduates

15%83%

Homes with flush toilets

10%98%

Homes with electricity

2%99%

Living in suburbs

10%

52%

Hourly manufacturing job wage (adjusted for inflation)

$3$15

Homicides per 100,000 people

1.25.8

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 ______________ force

• ________ of raising and educating children

• Availability of private and public ___________________

• Urbanization – better access to family _____________ services

• Educational and employment opportunities for women…better educated women tend to marry ___________ and have ____________ children

labor

Cost

pensions

planning

laterfewer

Several Factors Affect Birth Rates and Fertility Rates (2)

• Average age of a woman at birth of _________ child

• Availability of legal _______________• Each year about 190 million become pregnant and at

least ______ million women get abortions

• Availability of reliable ________________ methods

• ______________ beliefs, traditions, and cultural norms

first

abortions

40

birth-control

Religious

Fig. 6-8, p. 132

Girl Carrying Well Water in India

In poorer countries,having more children helps a family to complete their daily _________ and survive

tasks

Fig. 6-9, p. 133

Child Laborers in India

Core Case Study

• In China, couples prefer to have a __________, because they are more likely to leave their family in the future

• Some Chinese couples abort female fetuses…which has lead to a __________ shortage

boy

bride

Several Factors Affect Death Rates (1)• 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 _________ year

• Why are people living longer?• Increased food _______________ and distribution• Better __________________• ____________________ advances• Improved ______________________

health

first

supplynutrition

medicalsanitation

Several Factors Affect Death Rates (2)• U.S. is 54th in world for infant mortality rate…• somewhat _______ for a MDC

• U.S. infant mortality rate high due to• Inadequate health care for ________ women during

pregnancy and their infants• Drug ________________ among pregnant women• High birth rate among ___________________

high

poor

addictionsteenagers

Fig. 6-10, p. 134

Infant Mortality Rates, 1950-2010

Migration Affects an Area’s Population Size

• Migration – movement into (immigration) or out of (emigration) a population

• Most migrating people are… • Seeking __________________ improvement• Seeking religious or political _______________• __________________ wars or environmental

problems (environmental __________________)

economicfreedoms

Escapingrefugees

Case Study: The United States: A Nation of Immigrants

• Currently, both legal and illegal immigration accounts for _________ of our annual population growth• Before 1960, most immigrants came from Europe• After 1960, most have __________________ and

_________________

• Controversy over immigration policy • _______ of the American public supports reducing

legal immigration• Reducing immigration will also affect our cultural

______________ and social security ______________

36%

Latin-AmericaAsia

60%

diversity benefits

Fig. 6-11, p. 135

Legal Immigration to the U.S. between 1820 and 2006

Review Questions

• What has happened to the world’s TFR since 1950? How has that affected our population growth?

• Why is the infant mortality rate in the U.S. higher than expected?

Has decreased….slowed our growth

Inadequate health care for poor women

Drug addictions

High teenage pregnancy rates