Parity progression ratios

Measure used in demography to study fertility

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 {\displaystyle a_{x}} , can be achieved by using the following formula:

a x = (women with at least x + 1 children ever born) / (women with at least x children ever born) {\displaystyle a_{x}={\text{(women with at least }}x+1{\text{ children ever born) }}/{\text{ (women with at least }}x{\text{ children ever born)}}} [1]

In more developed countries where two-child families are seen as the norm  a 2 {\displaystyle 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 {\displaystyle a_{0}} is simply the proportion of women who become mothers.

## References

[edit]

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