A Projection of Australian Fertility Using a Three-Parameter Model

Meimanat Hosseini Chavoshi, University of Melbourne
Peter McDonald, University of Melbourne

The usual approach to projecting births uses historical fertility trends by age to predict future rates. However, fertility is relatively more predictable if, in addition to the woman’s age, it is based on parity a woman has already and time since the previous birth. Using the 2016 and 2021 Australia censuses, this paper employs a three-parameter model to forecasting births in Australia in the 2020s. Estimates of three-parameter birth rates during 2016-2021 and the 2021 are used in the model to forecast births. Additionally, the three-parameter approach enables the construction of a range of useful indicators of fertility trends. By converting the rates to probabilities, the probability that a woman who is childless at age x will have a baby at different times in the future can be calculated. Likewise, the second and higher order birth probabilities controlling for time since the previous birth can be estimated. The period probability of having a first birth by the end of reproductive life was %80.5, %67.9 of women at age 30 have their first birth, and having first birth falling to %11 at age 40. The probabilities based on the three-parameters will be presented in the full paper along with the forecasts.

Keywords: Fertility, Population projections, forecasts, and estimations, Census data

See extended abstract.