Parity progression ratios explained

A parity progression ratios (PPR) is a measure commonly used in demography to study fertility. The PPR is simply the proportion of women with a certain number of children who go on to have another child. Calculating the PPR, also known as

a _{x} , can be achieved by using the following formula:a _{x} = (womenwithatleast x +1 childreneverborn) / (womenwithatleast x childreneverborn) ^[1]

In more developed countries where two-child families are seen as the norm

a _{2} (or the proportion of women with two children who go on to have a third) is of critical importance in determining overall fertility levels.a _{0} is simply the proportion of women who become mothers.

Notes and References

1. Hinde, A (1998) "Demographic Methods", Hodder Arnold Publication.