Demography
April 30, 2008
http://www.iastate.edu/~soc.134
© 2008 David Schweingruber
Birth cohorts
 Birth cohort: set of people who were born during the same era and who
face similar societal circumstances brought about by their shared
position in the overall age structure of the population (p. 463)
 Birth cohorts effect everyday lives in two ways:
• Cohort effect: phenomenon in which members of a birth cohort tend to
experience a particular life event or rite of passage—puberty, marriage,
childbearing, graduation, entry into the workforce, death—at roughly the
same time (p. 463)
• Period effect: phenomenon in which a historical event or major social trend
contributes to the unique shape and outlook of a birth cohort (p. 464)
©©2008
2000David
DavidSchweingruber
Schweingruber
2.5%
High immigration
& birth rates
250,000
Baby boom
2.0%
200,000
1.5%
150,000
1.0%
0.5%
Great Depression,
low immigration
Population
Growth rate
50,000
0.0%
1995
1990
1985
1975
1970
1965
1960
1955
1950
1945
1940
1935
-0.5%
1930
1925
1915
1910
1905
0
1920
1918 flu
epidemic
1980
100,000
Annual growth rate
300,000
1900
U.S. population (thousands)
U.S. population & growth rates,1900-98
©©2008
2000David
DavidSchweingruber
Schweingruber
Total births & birth rates in U.S., 1910-95
Baby boom
45
Echo boom
4,000,000
40
35
Depression
Generation
3,000,000
30
Baby bust
2,500,000
2,000,000
25
20
GI Generation
War babies
1,500,000
15
1,000,000
10
Total births
500,000
5
Birth rate
1995
1990
1985
1980
1975
1970
1965
1960
1955
1950
1945
1940
1935
1930
1925
1920
0
1915
0
1910
Total births
3,500,000
Births per 1,000 people
4,500,000
©©2008
2000David
DavidSchweingruber
Schweingruber
Some generational labels
GI Generation (“Greatest Generation”): 1910-1924
Silent Generation: 1925-1945
Baby Boomers: 1946-1964
• Generation Jones (1954-1964)
Baby Busters (Gen X): 1965-1981
Echo Boomers (Millennials, Gen Y): 1982-1994
Generation Z (1995-)
©©2008
2000David
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Schweingruber
Presidential Candidate Generations
 GI Generation: Six presidents born between
1911-1924
 The Silent Generation: No presidents between
1925-1945
• John McCain (b. 1936)
 Baby Boomers: Clinton and G.W. Bush born in
1946
• Hillary Clinton (b. 1947)
 Generation Jones
• Barak Obama (b. 1961)
©©2008
2000David
DavidSchweingruber
Schweingruber
Malthusian theory
Thomas Malthus (1766-1834) claimed that
population increases geometrically (2, 4, 8, 16…),
but food production increases arithmetically (2, 3, 4,
5…)
• The result will be worldwide starvation
Malthusʼ predictions proved wrong
 Population growth rates donʼt always increase
 Food production has kept pace with population increase
©©2008
2000David
DavidSchweingruber
Schweingruber
Demographic transition theory
 Demographic transition: stage of societal development in unindustrialized
countries marked by growing life expectancy and high birthrates; concept
used to explain why populations in less-developed countries grow faster
than those in more developed countries (p. 473)
 Three stages
• Stage 1 (preindustrial): slow growth because of very high birth and death rates
• Stage 2 (early industrial): Rapid growth because death rate drops, but birth
rate remains high
• Stage 3 (later industrial): Slow growth because birth rate drops to approach
death rate
©©2008
2000David
DavidSchweingruber
Schweingruber
Consequences of demographic transition
 Most worldwide population growth happened in past 200
years
• First billion reached in 1804, sixth billion in 1999, 6.5 billion in 2005
• UN estimated range is 7.6-10.6 billion by 2050
 World population growth is stabilizing
• Highest growth rate (2.04%) in late 1960s; now at 1.21%
• U.N. projects rate of 0.37% by 2045-50
• U.N. projects total fertility rate of 2.05 by 2045-50
 Growth rates vary among nations
• Most growth is in developing nations (1.4% annual growth)
• Most developed nations approach or are below zero population
growth (ZPG)
 Age structures and sex ratios vary among nations
©©2008
2000David
DavidSchweingruber
Schweingruber
Birth rates/death rates of six nations, 1998
Births/deaths per 1,000
people
60
Birth rate
Death rate
53.0
50
42.4
40
30
20
23.4
17.4
14.4
8.8
10
0
Niger (2.9%) Afghanistan U.S. (1.0%)
(5.9%)
12.1
11.710.8 9.7 9.6
7.3
Canada
(1.2%)
Sweden
(0.4%)
Spain (0.1%)
Nations (with annual growth rate)
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2000David
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Schweingruber
Total fertility rates of selected nations, 2000-05
At or approaching ZPG
Hong Kong
0.94
Ukraine
1.12
Czech
1.17
South Korea
1.23
Bulgaria
1.24
Italy
1.28
Germany
1.32
Canada
1.51
United Kingdom
1.66
Australia
1.75
Russia
2.03
United States
2.04
Higher TFR
Niger
Afghanistan
D.R. of Congo
Yemen
Zambia
Kenya
Sudan
Haiti
Egypt
India
South Africa
Mexico
7.91
7.48
6.70
6.20
5.65
5.00
4.45
3.98
3.39
3.07
2.80
2.40
©©2008
2000David
DavidSchweingruber
Schweingruber
Age structures in six nations, 2005
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
3.8%
7.9%
15.7%
17.9%
62.5%
64.5%
26.3%
25.6%
59.7%
60.4%
45.7%
60.0%
50.5%
32.1%
Uganda
(14.8)
India
(24.3_)
20.8%
17.6%
14.0%
14.0%
U.S.
(36.1)
Canada
(38.6)
Japan
(42.9)
Italy
(42.3)
0-14
15-59
60+
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2000David
DavidSchweingruber
Schweingruber
Sex ratios
 Sex ratio at birth: 105 males to 100 females
 Sex ratio for world population: 101
 Nations with older populations have fewer men than women
because women live longer
• E.g., Italy 94 sex ratio, Spain 95, Japan 96, U.S. 97
 Other nations have more men than women because
women are selectively aborted, neglected or killed
•
•
•
•
China (106 sex ratio) has one-child policy
India (105) has dowry tradition
Afghanistan (107) limited womenʼs medical care under Taliban
Highest ratios are on Arabian Peninsula, including UAE (214), Qatar
(206), Oman (128), and Saudi Arabia (117)
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2000David
DavidSchweingruber
Schweingruber