6 Breastfeeding should not be used as a primary method of birth control. Couples tend to overproduce in order to achieve their desired family size after discounting for a possible child death. In societies or families with a strong gender preference, some couples end up having many more children than they would have wanted had they achieved the preferred gender composition sooner. Fertility rates are eventually shaped by couples' wish to avoid or delay having children, or properly spacing them through use of contraception. A myriad of socioeconomic factors such as concern for quality of life, alternative sources of satisfaction, and alternative use of time in activities such as earning money, pursuing higher education, and pursuing alternative activities operate in this relationship between income and fertility.
Education is associated with delayed marriage, which in itself delays fertility.
It also operates through concern for quality of children, and alternative sources of satisfaction such as job and career.