DEMOGRAPHIC TRANSITIONWhile demographers argue about the details
of demographic change in the past 200 years,
clearcut declines in birth and death rates appeared
on the European continent and in areas of over-
seas European settlement in the nineteenth centu-
ry, especially in the last three decades. By 1900, life
expectancies in ‘‘developed’’ societies such as the
United States were probably in the mid-forties,
having increased by a few years in the century
(Preston and Haines 1991). By the end of the
twentieth century, even more dramatic gains in
mortality were evident, with life expectancies reach-
ing into the mid- and high-seventies.
The European fertility transition of the late
1800s to the twentieth century involved a relatively
continuous movement from average fertility levels
of five or six children per couple to bare levels of
replacement by the end of the 1930s. Fertility
levels rose again after World War II, but then
began another decline about 1960. Some coun-
tries now have levels of fertility that are well below
long-term replacement levels.
With a few exceptions such as Japan, most
other parts of the developing world did not experi-
ence striking declines in mortality and fertility
until the midpoint of the twentieth century. Gains
in life expectancy became quite common and very
rapid in the post-World War II period throughout
the developing world (often taking less than twen-
ty years), although the amount of change was quite
variable. Suddenly in the 1960s, fertility transi-
tions emerged in a small number of societies,
especially in the Caribbean and Southeast Asia, to
be followed in the last part of the twentieth centu-
ry by many other countries.
Clear variations in mortality characterize many
parts of the world at the end of the twentieth
century. Nevertheless, life expectancies in coun-
tries throughout the world are generally greater
than those found in the most developed societies
in 1900. A much greater range in fertility than
mortality characterizes much of the world, but
fertility declines seem to be spreading, including
in ‘‘laggard’’ regions such as sub-Saharan Africa.
The speed with which the mortality transition
was achieved among contemporary lesser-devel-
oped countries has had a profound effect on the
magnitude of the population growth that has oc-
curred during the past few decades. Sweden, a
model example of the nineteenth century Europe-
an demographic transition, peaked at an annual
rate of natural increase of 1.2 percent. In contrast,
many developing countries have attained growth
rates of over 3.0 percent. The world population
grew at a rate of about 2 percent in the early 1970s
but has now declined to about 1.4 percent, as
fertility rates have become equal to the generally
low mortality rates.CAUSES OF MORTALITY TRANSITIONSThe European mortality transition was gradual,
associated with modernization and raised stan-
dards of living. While some dispute exists among
demographers, historians, and others concerning
the relative contribution of various causes (McKeown
1976; Razzell 1974), the key factors probably in-
cluded increased agricultural productivity and im-
provements in transportation infrastructure which
enabled more efficient food distribution and, there-
fore, greater nutrition to ward off disease. The
European mortality transition was also probably
influenced by improvements in medical knowl-
edge, especially in the twentieth century, and by
improvements in sanitation and personal hygiene.
Infectious and environmental diseases especially
have declined in importance relative to cancers
and cardiovascular problems. Children and in-
fants, most susceptible to infectious and environ-
mental diseases, have showed the greatest gains in
life expectancy.The more recent and rapid mortality transi-
tions in the rest of the world have mirrored the
European change with a movement from infec-
tious/environmental causes to cancers and cardio-
vascular problems. In addition, the greatest bene-
ficiaries have been children and infants. These
transitions result from many of the same factors as
the European case, generally associated with eco-
nomic development, but as Preston (1975) out-
lines, they have also been influenced by recent
advances in medical technology and public health
measures that have been imported from the high-
ly-developed societies. For instance, relatively in-
expensive vaccines are now available throughout
the world for immunization against many infec-
tious diseases. In addition, airborne sprays have
been distributed at low cost to combat widespread