Explanations for fertility levels and trends
This page lists some broad categories of explanations for fertility levels and trends, as well as typologies to classify and explain the trends.
Classifications of explanations for fertility
Classifications based on what measure of desire or expectation it is reflected in
Consider the distinction between:
- Ideal family size (social): The number of children people believe a family should have.
- Desired fertility (individual): The number of children people want indivdually.
- Expected fertility (or intended fertility): The number of children people expect to have, after accounting for their limitations.
- Completed fertility: The number of children people finally end up having.
For young people, expected fertility starts out close to desired fertility. As people near the end of childbearing years, expected fertility approaches completed fertility.
Explanations for fertility levels can be distinguished based on their predictions for each of these measures. For instance, a decline of a pronatalist belief system (such as a pronatalist religion) would affect all the measures, including ideal family size. On the other hand, rising costs of childbearing would lead to a decline in expected fertility and completed fertility relative to ideal family size.
Classification of the stage of operation
- Some mechanisms operate at a stage prior to conception. Examples are mechanisms that affect people's ability to find suitable marital partners or partners for other arrangements within which childrearing is conventionally done.
- Some mechanisms operate in the stages from conception to birth. These include mechanisms related to abortion, contraception, infertility treatment, prenatal and neonatal care.
- Some mechanisms operate in relation to life after the child's birth. These can further be classified based on the child's birth stage.
Note that this mode of classification is somewhat correlated with the preceding mode of classification, but the correlation is not perfect.