As countries develop, the economic and social betterment takes place. In previous times, women were considered more appropriate for taking care of household chores and bearing & rearing children. Consequently, women were not active participants in the job market and since women were at home for childcare, the birth rate was naturally high.

However, since now women have more economic opportunities available, they take up jobs and bear lesser number of children.

One plausible explanation for this can be the costs associated with child care. If a woman is working, she must pay for child care facilities. Thus, in this case there are additional costs of having a child. Therefore, she might decide to have lesser number of children or not having them altogether.

This explains the economic rationale for the pattern of falling birth rates as incomes and economic opportunities for women have increased.