The case for parity and birth-order statistics

Parity refers to the number of (live) births that a woman (or man) has had. Birth order refers to whether a birth is the first, second, third or higher-order birth of the parent. In the context of low and shifting fertility, parity and birth-order statistics are becoming increasingly important for understanding fertility trends and patterns, for policy, and for carrying out projections of future fertility. In Australia, the main sources of demographic data are birth, death and marriage registers, and the five-yearly national census. Both the birth registers and the census are ideally placed to collect data required to calculate parity and birth-order statistics. However not all Australian states and territories collect or code the necessary information in the birth registers, and the parity question 'For each female, how many babies has she ever had' is only asked every second census; that is, once every 10 years. In this paper, we outline the importance and uses of parity and birth-order statistics. We discuss the Australian data available at present and their gaps and shortcomings. We then describe the 'gold standard' of parity and birth-order statistics and how Australia can achieve this standard through some minor changes to the data collection process.