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 interest to demographers for a long time. Presenting our detailed study of period fertility in Austria since 1984, we discuss the problems and advantages of constructing and analysing monthly series of various period fertility indicators that reflect real exposure and potentially minimise the distortions caused by changes in fertility timing. We correct monthly birth data for calendar and seasonal factors and show that seasonality of births in Austria varies by birth order. Our study suggests that most of the timing distortions can be eliminated when using an indicator derived from the period parity progression ratios based on birth interval distributions, termed the "period average parity" (PAP). We illustrate the insights gained with the PAP and compare this with the commonly used total fertility rates in an analysis of the recent upswing in period fertility, starting in the late 2001. This investigation will be useful in establishing a monitoring of monthly fertility rates in Austria.