Several historic events give the age-sex pyramid of
the total US population its unique shape. The most striking feature is
the “baby
boom,” the
increase in the number of people born after World War II between
1946 and 1964. In 2000, the baby boomers were between age 35 and 54, as can be
seen by the relatively large size of those age groups in the age-sex pyramid.
The years 1965 to about 1977 are often referred to as the “baby bust” because
of the smaller number of children born then. The “baby bust” generation
was between the ages of 23 and 35 in 2000, as can be seen by the
constriction of those age groups in the age-sex pyramid. The “echo
boom” or “boomlet” occurred
between 1977 and about 1988, when many of the baby boomers had children
who, in 2000, were between 12 and 23. Fertility in the United States
declined after 1995, as indicated by the constriction of the pyramid’s
base and the relatively smaller number of people under the age of
five. In the older age groups, there are far fewer males than females.
In most populations, women live longer than men. The dearth of males
age 70 and older also reflects deaths during World War II.
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