Coale Fertility Indices

Coale's fertility indices are a set of standardized measures — If (overall fertility), Ig (marital fertility), Ih (nonmarital fertility), and Im (proportion married, an index of marriage) — that express a population's childbearing relative to the highest reliably recorded natural-fertility schedule, that of the Hutterites. Devised by Ansley Coale for the Princeton European Fertility Project, they hold the maximum age schedule of fertility fixed so that differences between populations reflect real differences in fertility and marriage rather than age structure, and they tie together into a single identity linking overall fertility to marriage and to fertility within and outside marriage.