Age- and parity-specific birth trends in Australia: Is low fertility inevitable?

Fertility in Australia has persistently remained below replacement level, raising the question of whether public policy can meaningfully influence birth behaviour or whether societies should instead adapt to sustained low fertility. Using population-wide data from the Victorian Perinatal Data Collection covering over two million births between 1983 and 2020, we construct 41 monthly birth-rate series by maternal age and parity and adopt a data-driven empirical strategy. Combining ARIMA modelling, Bai–Perron structural break tests, interrupted time-series estimation with gestation-consistent lags, and local regression-discontinuity-in-time diagnostics, we identify cohort-specific turning points without imposing policy dates ex ante and assess their alignment with major national family policies. We find robust structural breaks only for second births, with short-lived upward shifts around 2005 and 2015 consistent with conceptions following the introduction and withdrawal of the Baby Bonus. These effects quickly dissipate, while other cohorts show little alignment with policy timing, suggesting that Australian family policy has mainly altered the timing of births rather than reversing the long-run fertility decline.