The Pace of Fertility Decline

Fertility has fallen by an average of 1% per year in the 38 developing countries surveyed more than once since 1990. The pace of change varies widely among countries, however—from Yemen, where the TFR fell by 1.2 children per woman in five years, to Niger, where the TFR rose by 0.2 children per woman in six years. Although generally fertility has been falling, surveys conducted since 1990 suggest that the pace of decline has been slowing compared with fertility declines in the 1970s and 1980s. Considering all countries that have had more than one survey, including surveys before 1990 as well as after, instances of slowing in the rate of fertility decline outnumber accelerations in the rate of decline by two to one.

Many factors help to explain why the pace of fertility decline appears to be slowing. Fertility declines faster when fertility rates are high (21), as was the case in many developing countries in the 1970s and 1980s. Meanwhile, economic and social changes, new information and ideas, new reproductive attitudes, smaller family size ideals, and access to effective contraception were spreading rapidly.

At the same time, infant and child mortality was falling in response to better public health measures in most countries. Family sizes increased as more children survived their first few years of life. Thus demand for fewer children and use of contraception grew, resulting in rapid declines in fertility.

By the start of the 1990s, in contrast, family planning information and services had become widespread throughout much of the developing world. Most people already knew about contraception and where to obtain it. Moreover, the influence of new social norms favoring smaller families had already been reflected in lower fertility rates. Much of the latent demand for family planning had been met. Given these trends and smaller family sizes compared with the 1970s and 1980s, it should not be surprising that, while fertility continued to decline in the 1990s in most countries, the pace of decline has been slower.

Prospects for further decline. Despite fertility declines, in a number of developing countries women still are having more children than they say they would prefer, and many still prefer larger families than women in developed countries. Thus there remains substantial scope for further fertility declines. Fertility can be expected to fall further as more women become better able to prevent unwanted births. In addition, future fertility levels are likely to depend increasingly on changes in social and economic factors that lead people in developing countries to desire fewer children (21).

In the coming years fertility is likely to decline fastest where it is now highest—that is, in sub-Saharan Africa. So far, the pace of fertility decline in sub-Saharan Africa has been considerably slower than in other developing regions, since on average African couples prefer to have more children than do couples elsewhere (29).

In the 1980s fertility started to decline in a few sub-Saharan countries—the beginning of a trend to smaller family preferences and more contraceptive use in the region. Nevertheless, during the 1990s many sub-Saharan countries were only starting their fertility transitions, leaving room for more rapid declines than elsewhere, where the fertility transition was more advanced (29).

The “tempo effect.” Recently, fertility appears to have stopped falling altogether in some developing countries (52). One reason is a demographic “tempo effect.” This effect results from changes in the timing of childbearing rather than the overall demand for children. It probably explains some of the apparent stalling of fertility decline in such countries as Bangladesh, Colombia, Egypt, Indonesia, and Turkey, although the magnitude of the tempo effect is difficult to estimate (18).

The tempo effect operates as follows: When the average age at which women give birth rises, the TFR appears to decline temporarily, even if women continue eventually to reach the same completed family size as before. When completed family size is falling at the same time that the average age at first birth is rising, as has been the case in the past few decades until recently, the TFR declines even faster (18).

But when the average age at which women have their first birth stops rising, as was the case in some countries during the 1990s, the TFR can temporarily stop its decline or even rise somewhat. This effect is completely independent of any changes in family size preferences or levels of contraceptive use.