Page 217 - Environment: The Science Behind the Stories

Male Female Male Female
100 100
90 90
80 80
70 70
60 60
Age 50 Age 50
40 40
30 30
20 20
10 10
0 0
2 1 0 1 2 15 12 9 6 3 0 3 6 9 12 15
Population (millions) Population (millions)
(a) Age structure diagram of Canada in 2012 (b) Age structure diagram of Nigeria in 2012

Figure 8.11 Canada (a) shows a fairly balanced age structure, whereas Nigeria (b) shows an age
distribution heavily weighted toward young people. Nigeria’s population growth rate (2.6%) is over six
times greater than Canada’s (0.4%). Data from United States Census Bureau International Database. http://www.census.gov/
population/international/data/idb/.

As an example, compare age structures for the nations On the other hand, a shift in age structure toward an
of Canada and Nigeria (Figure 8.11). Nigeria’s large concen- older population reduces the proportion of dependent chil-
tration of individuals in young age groups portends a great dren. Fewer young adults may mean a decrease in crime
deal of reproduction. Not surprisingly, Nigeria’s population rates. Moreover, older people are often productive mem-
growth rate is much greater than Canada’s. bers of society, contributing volunteer activities and ser-
Today, populations are aging in many nations (Figure 8.12). vices to their children and grandchildren. In many ways
The global median age today is 28, but it will be 38 in the year both good and bad, “graying” populations will affect socie-
2050. Population aging is pronounced in the United States, ties in China, the United States, Europe, and other nations
where the “baby boom” generation is now approaching retire- throughout our lifetimes.
ment age. In coming years you will likely be required to pay
more taxes to support Social Security and Medicare benefits
for your elders. 25 Number of people Percent of global 25
By causing dramatic reductions in the number of chil- aged 15–64 for population aged
dren born since 1970, China’s one-child policy virtually 20 each person aged 60 or over 20
guaranteed that the nation’s population age structure would 65 and over
change. Indeed, in 1970 the median age in China was 20; by
2050 it will be 45. In 1970 there were more children under 15 15
age 5 than people over 60 in China, but by 2050 there will be 12 Number of people aged 15–64 for each person aged 65 and over Percent of global population aged 60 or over
times more people over 60 than under 5! Today there are 10 10
121 million Chinese people older than 65, but that num-
ber will triple by 2050 (Figure 8.13). This dramatic shift in 5 5
age structure will challenge China’s economy, health care
system, families, and military forces because fewer work-
ing-age people will be available to support social programs 0 1950 1975 2012 2025 2050 0
to assist the rising number of older people. In response, Year
China has recently taken small steps to loosen its repro-
ductive policies to increase its proportion of young people. Figure 8.12 Populations are aging worldwide as people
For example, if both the man and the woman in an urban of “baby boom” generations grow older and as birth rates
couple are single children, then they are permitted to have decline. As the percentage of the global population that is over
60 increases, fewer working-age people are available to support
a second child. the elderly. Data from Population Division of the Department of Economic
On the one hand, older populations will present new chal- and Social Affairs of the United Nations Secretariat, 2009. World population
lenges for many nations as increasing numbers of elderly will prospects: The 2008 revision. http://esa.un.org/wpp. © United Nations, 2009.
require the care and assistance of relatively fewer working- By permission. 2012 update from United States Census Bureau International
216 age citizens. Database. http://www.census.gov/population/international/data/idb/.

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