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6-2 What Factors Influence the Size of the Human Population?

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1 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.

2 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

3 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 fertility mortality

4 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 2.5 die

5 Reaching replacement level-fertility rates does _____ immediately halt population growth….you have to wait for ____________ girls to move through their reproductive years NOT young

6 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

7 Total fertility rate, 1955-2010 Which type of country has shown
the greatest drop in TFR? LDC Figure 6.5: This graph tracks the total fertility rate for both the more-developed and less-developed regions of the world, 1955–2010, with projections to 2050 (based on medium population projections). Although the world’s average TFR has dropped to 2.5, it will have to drop to around 2.1 to eventually halt the world’s population growth. (Data from United Nations Population Division) Fig. 6-5, p. 130

8 Total Fertility Rate Figure 12, Supplement 8

9 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 _______) 76 310 “baby boom” 79 3.7 2.1 slowed 1.5

10 Baby boom (1946–64) Replacement level
4.0 3.5 3.0 Births per woman 2.5 2.1 2.0 1.5 Baby boom (1946–64) Replacement level 1.0 0.5 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 Year Births per thousand population Figure 6.6: The top graph shows the total fertility rates for the United States between 1917 and 2010 and the bottom graph shows the country’s birth rate between 1917 and Question: The U.S. fertility rate has declined and remained at or below replacement levels since So why is the population of the United States still increasing? (Data from Population Reference Bureau and U.S. Census Bureau) End of World War II Demographic transition Depression Baby boom Baby bust Echo baby boom 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 Year Fig. 6-6, p. 131

11 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 ecological foootprint

12 2010 Rate of Population Increase
Figure 11, Supplement 8

13 Married women working outside the home 8% 81%
77 years Life 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 1.2 5.8 Stepped Art Fig. 6-7, p. 132

14 Since our ecological footprint is too large, many demographers consider the U.S. to be _____________________ overpopulated

15 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 later fewer

16 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

17 Girl Carrying Well Water in India
In poorer countries, having more children helps a family to complete their daily _________ and survive tasks Figure 6.8: This girl is carrying well water across parched earth that has dried out and cracked during a severe drought in India. Fig. 6-8, p. 132

18 Child Laborers in India
Figure 6.9: These young girls are child laborers in the state of Rajasthan in India. They are weaving wool on looms to make carpets for export, and receive very little money for their work. Fig. 6-9, p. 133

19 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

20 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 supply nutrition medical sanitation

21 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 addictions teenagers

22 Infant Mortality Rates, 1950-2010
Figure 6.10: This graph tracks the infant mortality rates for the world’s more-developed countries and less-developed countries, 1950–2010, with projections to 2050 based on medium population projections. (Data from United Nations Population Division) Fig. 6-10, p. 134

23 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 __________________) economic freedoms Escaping refugees

24 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-America Asia 60% diversity benefits

25 Legal Immigration to the U.S. between 1820 and 2006
Figure 6.11: This graph shows legal immigration to the United States, 1820–2006 (the last year for which data are available). The large increase in immigration since 1989 resulted mostly from the Immigration Reform and Control Act of 1986, which granted legal status to certain illegal immigrants who could show they had been living in the country prior to January 1, (Data from U.S. Immigration and Naturalization Service and the Pew Hispanic Center) Fig. 6-11, p. 135

26 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

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