Sub-replacement Fertility - Effects

Effects

Further information: Dependency ratio and Pensions crisis

Sub-replacement fertility does not immediately translate into a population decline because of population momentum: recently high fertility rates produce a disproportionately young population, and younger populations have higher birth rates. This is why some nations with sub-replacement fertility still have a growing population, because a relatively large fraction of their population are still of child-bearing age. But if the fertility trend is sustained (and not compensated by immigration), it results in population ageing and population decline. This is forecast for most of the countries of Europe and East Asia.

Current estimates expect the world's total fertility rate to fall below replacement levels by 2050, although population momentum will continue to increase global population for several generations beyond that. The promise of eventual population decline helps reduce concerns of overpopulation, but many believe the Earth's carrying capacity has already been exceeded and that even a stable population would not be sustainable.

Some believe that not only this (apparent) economic depression we have entered, but the 'Great Depression' of the 1930's (and beyond?) may be, and may have been, the result of a decline in birthrates overall. Clarence L. Barber, an economist at the University of Manitoba, pointed out how demand for housing in the US, for example, began to decline in 1926, due to a decline in 'household formation' (marriage), due, he believed, to the effects of World War I upon society. In early 1929, US housing demand declined precipitously. And, of course, the stock market crash followed in October of that same year.

Even though the overall world population continues to increase, it is more at the 'back end' than the 'front end' that this is occurring. That is, more people are kept alive than in the past due to improved nutrition, more refrigeration and better sanitation worldwide, as well as health care advances, from vaccines to antibiotics, and many other advances in medications and in different improvements in health care. Certainly, in advanced nations, few groups would be considered to be "breeding like rabbits". The 'baby boom' (1946-1964) in the US, was likely, if Barber's contentions are correct, more of a return to birthrates closer to historical norms, like those of the first decade of the 20th century (but the 'baby boom' of 1946-1964 were still lower than the 1900-1910 period), with birth dearths both before and since making the so-called "baby boom" appear so big.

Sub-replacement fertility can also change social relations in a society. Fewer children, combined with lower infant mortality has made the death of children 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 the number of siblings, aunts and uncles and other extended family members.

Population aging may pose an economic challenge to governments as the number of retired citizens drawing public pensions rises in relation to the number of workers. This has been raised as a political issue in France, Germany, and the United States where many people have advocated policy changes to encourage higher birth and immigration rates. In France, payments to couples who have children have increased birth rates.