Environmental Engineering Reference
In-Depth Information
Figure 7-5
Some major changes that
took place in the United States be-
tween 1900 and 2000. (Data from U.S.
Census Bureau and Department of
Commerce)
47 years
Life expectancy
77 years
8%
Married women working
outside the home
81%
15%
High school
graduates
83%
10%
Homes with
flush toilets
98%
developed countries since 1950, most of
which are expected to have declining
populations after 2010. Because of its
high per capita rate of resource use, each
addition to the U.S. population has an
enormous environmental impact (Fig-
ure 1-7, p. 11, and Figure 3 in Sci-
ence Supplement 2 at the end of
this topic). In addition to the al-
most fourfold increase in popu-
lation growth, some amazing
changes in lifestyles took place in the
United States during the 20th century
(Figure 7-5).
2%
Homes with
electricity
99%
10%
Living in
suburbs
52%
1900
$3
Hourly manufacturing job
wage (adjusted for inflation)
2000
$15
1.2
Homicides per
100,000 people
5.8
paid employment outside the home. In developing
countries, women with no education generally have
two more children than women with a secondary
school education.
Another factor is the
infant mortality rate.
In areas
with low infant mortality rates, people tend to have a
smaller number of children because fewer children die
at an early age.
Average age at marriage
(or, more precisely, the av-
erage age at which women have their first child) also
plays a role. Women normally have fewer children
when their average age at marriage is 25 or older.
Birth rates and TFRs are also affected by the
avail-
ability of legal abortions.
Each year about 190 million
women become pregnant. The United Nations and the
World Bank estimate that 46 million of these women
get abortions—26 million legal and 20 million illegal
(and often unsafe).
The
availability of reliable birth control methods
(Fig-
ure 7-6) allows women to control the number and spac-
ing of the children they have.
Religious beliefs, traditions,
and cultural norms
also play a role
.
In some countries,
these factors favor large families and strongly oppose
abortion and some forms of birth control.
Factors Affecting Birth Rates
and Fertility Rates
The number of children women have is affected by the
cost of raising and educating children, educational
and employment opportunities for women, infant
deaths, marriage age, and availability of
contraceptives and abortions.
Many factors affect a country's average birth rate and
TFR. One is the
importance of children as a part of the la-
bor force.
Proportions of children working tend to be
higher in developing countries—especially in rural ar-
eas, where children begin working to help raise crops
at an early age.
Another economic factor is the
cost of raising and
educating children.
Birth and fertility rates tend to
be lower in developed countries, where raising chil-
dren is much more costly because they do not enter the
labor force until they are in their late teens or twenties.
The
availability of private and public pension systems
affects how many children couples have
.
Pensions re-
duce parents' need to have many children to help sup-
port them in old age.
Urbanization
plays a role. People living in urban
areas usually have better access to family planning ser-
vices and tend to have fewer children than those living
in rural areas, where children are often needed to per-
form essential tasks.
Another important factor is
the educational and em-
ployment opportunities available for women.
TFRs tend to
be low when women have access to education and
Factors Affecting Death Rates
Death rates have declined because of increased food
supplies, better nutrition, advances in medicine,
improved sanitation and personal hygiene, and safer
water supplies.
