Sub-replacement fertility is a fertility rate that is not high enough to replace an area's population. Sub-replacement fertility is below approximately 2.1 children per woman's life time. (Note: 2.1 children per woman includes 2 children to replace the parents, with one-tenth of a child extra to make up for the mortality of children and of women who do not reach the end of their reproductive years.)
Today about half the world lives in nations with sub-replacement fertility. All the nations East Asia, with the exceptions Mongolia, the Philippines, and Laos are below. Russia and Eastern Europe are in most cases quite dramatically below replacement fertility. Western Europe also is below replacement. In the Middle East Iran, Tunisia, Algeria, Turkey, and Lebanon are below replacement. Canada, Australia, and New Zealand are similar to Western Europe, while the United States is just barely below replacement with about 2.0 births per woman. All four of these nations still have growing populations due to high rates of immigration. The countries having the lowest fertility are Hong Kong, Macao, Singapore and Lithuania.
There have been a number of explanations for the general decline in fertility rates in much of the world, and the true explanation is almost certainly a combination of different factors.
The increase of urbanization around the world is considered by many a central cause. Throughout human history urban areas have had below replacement fertility. Cities have higher land values, making a large family more expensive, the need for extra labour from children is also far less useful than on farms. Higher rates of disease also reduce urban fertility somewhat. Rural areas also tend to be more conservative with less contraception and abortion than urban areas.
Changes in contraception are also an important cause, and one that has seen dramatic changes in the last few generations. Abortion has been legalized in much of the world and contraception has become far more accepted. Whether this is a base cause of declining fertility, or merely a manifestation of the economic pressures of urbanization and the social changes brought about by the role of women is still debated.
The rise of feminism is also viewed as a crucial cause by many. Growing female participation in the work force has led to many women delaying or deciding against having children, or to not have as many. A longer pursuit of education also delays marriages. Greater female control of their own bodies combined with access to abortion and contraception also can reduce rates.
Other social changes both separate and related to feminism also have played a role. Bearing children is regarded as less of a social duty than it once was in many societies. A number of governments such as those of China and Iran have launched programs to reduce fertility rates and curb population growth.
Another school of thought argues that all these factors are a natural outgrowth of a Malthusian attempt to restore a population balance that was upset earlier. The revolution in hygiene and medicine that caused death rates to plummet during the twentieth century did not see a corresponding fall in birth rates until a couple generations later. This period of low death rates and high birth rates thus caused human population to balloon at a rate never before seen in human history on such a wide scale. The Malthusians argue that modern low birth rates are an attempt to counter act this imbalance.
The two main effects of sub-replacement fertility are population decline and population ageing. Population decline and ageing will occur in any society that does not see enough immigration to make up for the natural decrease. According to current trends this situation is the future for most of the countries of Europe and East Asia, most of which are reluctant to accept large numbers of immigrants.
Despite half the world's population having below replacement fertility the world's population is still growing quickly due to those nations with above replacement fertility often having rates considerably higher, and the fact that many of the women who will have their 2.1 children or fewer are alive but have not yet reproduced. A nation like Iran has below replacement fertility but the population will grow quickly over the next few years as so much of the population is still below eighteen and do not yet have their own families.
In the long term current trends in Iran, and the world as a whole, will see population stabilize, certainly by 2050, and we may even begin to see a global decline in human numbers. This has reduced fears of a crisis in world overpopulation, even though certain areas of the world, such as South Asia, still face problems due to high numbers of people.
Sub-replacement fertility can also greatly change social relations in a society. Fewer children tends to mean each child gets more attention from the parent. Fewer children, combined with lower infant mortality has also made the death of children in a far greater tragedy in the modern world than it was just fifty years ago. Having many families with only one or two children also reduces greatly the number of siblings, aunts and uncles. The family is central to all societies and this change will have deep effect social structure.
Population aging may pose an economic burden on societies, as the number of elderly retirees rises in relation to the number of young workers.
The American exception
While almost all of the developed world, and many other nations, have seen plummeting fertility rates over the last twenty-years, the United States' rates have remained stable and even slightly increased. A regional breakdown shows that New England has a rate similar to Western Europe and the South and border states have fertility rates considerably higher than replacement. States where the LDS Church has a strong presence, most notably Utah, also have higher-than-replacement fertility rates, especially among the LDS population.
There are a number of explanations for this. America's religious makeup limits participation in modern sex education and abortion. Statistically almost all of the difference between the United States and Europe can be explained by the States' vastly higher rate of teenage pregnancy. The United States also is somewhat more rural than Europe or Japan.
Last updated: 05-23-2005 19:49:44