Page 218 - Environment: The Science Behind the Stories

Male Female Male Female
100 100
90 90
80 80
70 70
Age 60 Age 60
50
50
40 40
30 30
20 20
10 10
0 0
70 60 50 40 30 20 10 0 10 20 30 40 50 60 70 70 60 50 40 30 20 10 0 10 20 30 40 50 60 70
Population (millions) Population (millions)
(a) Age structure diagram of China in 2012 (b) Projected age structure diagram of China in 2025

(c) Young female factory workers in Hong Kong (d) Elderly Chinese
Figure 8.13 As China’s population ages, older people will outnumber the young. Population pyramids
show the predicted graying of the Chinese population from 2012 (a) to 2025 (b). Today’s children may, as
working-age adults (c), face pressures to support greater numbers of elderly citizens (d) than has any previous
generation. Data in (a) and (b) from United States Census Bureau International Database. http://www.census.gov/population/
international/data/idb.

Sex ratios The ratio of males to females also can affect In recent years, demographers have witnessed an unset-
population dynamics. Note that population pyramids give tling trend in China: The ratio of newborn boys to girls has
data on sex ratios by representing numbers of males and become strongly skewed. Today, roughly 120 boys are born
females on opposite sides of each diagram. To understand the for every 100 girls. Some provinces have reported sex ratios
consequences of sex ratio variation, imagine two islands, one as high as 138 boys for every 100 girls. The leading hypoth-
populated by 99 men and 1 woman and the other by 50 men esis for these unusual sex ratios is that many parents, having
and 50 women. Where would we be likely to see the great- learned the sex of their fetuses by ultrasound, are selectively
est population increase over time? Of course, the island with aborting female fetuses.
an equal number of men and women would have a greater Recall that Chinese culture has traditionally valued
number of potential mothers and thus a greater potential for sons over daughters. Sociologists maintain that this cul-
population growth. tural gender preference, combined with the government’s
The naturally occurring sex ratio at birth in human popu- one-child policy, has led some couples to selectively abort CHAPTER 8 • Hum A n Po P ul AT i on
lations features a slight preponderance of males; for every female fetuses or to abandon or kill female infants. The
100 female infants born, about 106 male infants are born. Chinese government reinforced this gender discrimination
This phenomenon is an evolutionary adaptation (p. 68) to the when in 1984 it exempted rural peasants from the one-child
fact that males are slightly more prone to death during any policy if their first child was a girl, but not if the first child
given year of life. It tends to ensure that the ratio of men was a boy.
to women will be approximately equal when people reach China’s skewed sex ratio may further lower population
reproductive age. Thus, a slightly uneven sex ratio at birth growth rates. However, it has the undesirable social conse-
may be beneficial. However, a greatly distorted ratio can lead quence of leaving large numbers of Chinese men single. Many
to problems. of these men find employment as migrant workers and tend to 217

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