Monthly Estimates of the Quantum of Fertility: Towards a Fertility Monitoring System in Austria

Short-term variations in fertility and seasonal patterns of childbearing have been of interestto demographers for a long time. Presenting our detailed study of period fertility in Austriasince 1984, we discuss the problems and advantages of constructing and analysing variousperiod fertility indicators that reflect real exposure and potentially minimise the distortionscaused by changes in fertility timing. We correct monthly birth data for calendar andseasonal factors and show that seasonality of births in Austria varies by birth order. Ourstudy reveals that the methods explicitly aimed at adjusting fertility rates for tempodistortions are not suitable for computing monthly fertility rates. However, most of thetiming distortions can be eliminated when using an indicator derived from the period parityprogression ratios based on birth interval distributions, termed the Period Average Parity(PAP). We illustrate the insights gained from PAP and compare it with the commonly usedtotal fertility rates in an analysis of the recent upswing in period fertility, starting in the late2001. This investigation will serve for establishing a monitoring of monthly fertility ratesin Austria