Iran's extraordinarily rapid fall of fertility (the total fertility rate fell from 7.0 in 1980
to 2.1 in 2000) has been confirmed by analysis of a number of surveys and of the
2001 Census. This is documented fully in a recent paper by Abbasi-Shavazi and
McDonald (2005) using age-specific fertility rates and total fertility rates at the
national and provincial levels, urban and rural, for single calendar years over the last
three decades. The observed pattern of decline is one in which fertility has fallen
simultaneously in all age groups and in all geographic settings, hence accounting for
the rapidity of the observed decline at the national level. Remaining geographic
differences in fertility relate not to the pattern or timing of fertility decline but to
initial differences in levels of fertility when the decline commenced and, to a lesser
extent, to the speed of decline. The authors argue that the nation's fertility is likely to
continue its decline as several provinces now have below replacement level fertility
and fertility is still falling in the remaining provinces that have relatively high fertility.
Single calendar year time trends in the total fertility rate allow a precise association of
the fertility decline to the timing of the momentous socio-political and population
policy shifts before and after the 1979 Islamic Revolution. These associations give
rise to an interpretation of the fertility decline that is dominated by the influence of
cross-sectional events. However, it is well known that trends in the cross-sectional
total fertility rate can be confounded by changes in the timing of births across
women's lifetimes (tempo) as well as by changes in the numbers of children that they
have by the time they end their childbearing (quantum). The issue arises as to whether
trends in alternative measures of fertility that control for the parity distribution rather
than the age distribution (age at first birth, age at last birth, parity progression ratios)
show the same timing associations of fertility decline with social or political changes
as observed for changes in the total fertility rate. To do this, we use the 2000 Iran
Demographic and Health Survey to calculate time trends in parity progression ratios
and measures of starting, spacing and stopping of childbearing during the last three
decades.