Fundamentals of epidemiology - an evolving text - Are you looking ...

ates. Similarly, bulges in the reproductive years often produce bulges at the bottom, since more
women of reproductive age usually translates into more births.
Denmark, 1998 (note change in scale)
Using the pyramid it is easy to see how a growing population becomes younger and the transition to
lower fertility makes it older. Widespread family planning makes new birth cohorts smaller, so that
the pyramid consists of a broad middle (persons born before the adoption of family planning) being
pushed upward by a narrower base. Initially this age distribution makes life easier for adults,
especially women, since effort and resources for childrearing and support are proportionally lower.
However, when the adults who first adopted family planning reach retirement age, there are fewer
younger people available to support them. Unless productivity and savings have risen sufficiently,
the society will be hard pressed to support its elderly members—an issue of concern in affluent
societies today.
The population pyramid for Iran has a number of distinctive features. Iran embraced family
planning in the 1960's, one of the first developing countries to do so. The Islamic revolution of
1979, however, regarded the family planning program as "pro-West" and dismantled the program.
Moreover, with the war with Iraq made population growth seem advantageous. When the war
ended and reconstruction became the priority, the government reversed its policy and inaugurated a
new family planning program with an extensive information campaign and, in 1993, powerful
economic disincentives for having more than three children. These measures reduced the total
fertility rate (see below) from 5.2 children in 1989 to 2.6 children in 1997. (This account is taken
from Farzaneh Roudi, Population Today, July/August1999). The jump in the birth rate following the
revolution can be seen in the large size of the 15-19 year-old band (born 1979-1983) compared to
the next older one; the subsequent curtailment of births shows up as a relatively small number of
children 4 years old and younger. (Note: these population pyramids come from the U.S. Bureau for
the Census International Database and were downloaded from the Population Bureau web site.)
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www.epidemiolog.net, © Victor J. Schoenbach 1999, 2000 3. Studying populations - basic demography - 35
rev. 1/17/2000, 8/16/2000, 3/9/2001