How Low Can Fertility Be? An Empirical Exploration

Abstract

This study examines the possibility of minimum fertility. The author assumes that minimum fertility in a population depends upon the share of women in a given cohort who cannot or do not want any children and the remainder having just 1 child. Data from Italy were used to construct minimum fertility levels. Regional cohort fertility data among a 1963 cohort yielded 17.9% of women remaining childless and a total fertility rate of 1.5; 1.2 for the northern region of Emilia-Romagna. Theoretically childlessness of 20-30% could result in a fertility rate of 0.70-0.80 as the lower limit for cohort fertility. The total period fertility rate will be constant if this level of cohort fertility and the age at birth remain constant. If the cohort mean age at birth rises then period fertility would be less. An example is given where total fertility remains constant with successive 5-year cohort fertility of 0.80 0.75 and 0.70 and increased mean age at birth from 30-32 years. The result is that the share of women who give birth at age 30 and older rises from the first to last cohort from 49% to 65%. The share of women who give birth at age 35 and older rises from 16% to 28%. Over a 50-year period constant cohort total fertility and a shifting mean age at birth period rates would first decline and then after a minimum is reached period rates would equal the level of cohort fertility. Very low fertility is sustainable over 10-20 years with adjustment to the declines in size of the labor force and rapid aging. After declines over 30-40 years adjustments would be more severe.