That means that each couple would have at least two children so that they would be replacing themselves. This has not been the case for some time in Japan and Italy, which will be the first to feel the effects of depopulation. Germany will begin to decline soon thereafter. The United States is not projected to suffer population decline because our own birth rate maintains a replacement level and immigration provides a tremendous influx of people with high fertility rates each year. There is no singular cause for the sudden population decline the industrialized world will experience.
Affluence is associated with smaller family size.
In addition, the entry of women into the workplace has played a significant role. Today, women are attending college and striving for their own careers. They marry later in life than their mothers and subsequently have fewer childbearing years. Pursuing a successful career often rules out having a large family because the amount of time needed for maternity leave is highly prohibitive. The legalization of abortion and the proliferation of birth control devices have also played their parts.