Parity progression ratio

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Definition

The term parity progression ratio (PPR) is typically used in the context of a cohort of females (such as a birth cohort) that has completed its childbearing years. Given such a cohort, and a nonnegative integer i, the parity progression ratio from birth order i to birth order i + 1 is defined as the ratio of the completed cohort fertility for that cohort for birth order i+1, to the completed cohort fertility for that cohort for birth order i.

Alternatively, the PPR describes the probability that a person in that cohort who has had i children will proceed to have an (i+1)^{th} child.