ABS birth statistics are sourced from birth registration systems administered by the state and territory Registrars of Births, Deaths and Marriages. These data are based on information provided on a registration form completed by the parent(s) of the child. The registration of a birth is compulsory under relevant state/territory legislation, and there is a nationally consistent legislative requirement that all births be registered within 60 days.
There is often an interval between the occurrence and registration of a birth (referred to as a registration 'lag'), which may be longer than the 60 days specified in the legislation. This may be due to either a delay by the parent(s) in submitting a complete form to the registry, or a delay by the registry in processing the birth. The point at which the registration date is assigned differs between state and territory Registrars, and should be considered when analysing birth statistics (see paragraph 12 of the Explanatory Notes for more information).
The effect of delays in the registration of births have been analysed in previous issues of Births, Australia, and highlighted in Chapter 5: Delayed birth registrations in Australia (Births, Australia, 2005) and Chapter 4: Delayed Indigenous birth registrations in Australia (Births, Australia, 2006). Findings from previous analysis of registration lags included:
- wide variation in average registration lag among states and territories;
- improvements to registration timeliness resulting from the clearance of an accumulation of registrations and changes to follow-up procedures introduced by the New South Wales Registry in 2005;
- general increases in the length of delay in registration between 1995 and 2005;
- age differences in mothers' propensity to delay a birth registration (such that in general, younger mothers are more likely to delay a birth registration than older mothers); and
- the higher proportion of delayed registrations of Indigenous births, compared with non-Indigenous births.
Delays in the registration of births may affect the quality of fertility rates, which may be underestimated during periods where the registration of births is delayed, and overestimated when these births are subsequently registered. In order to examine the effect of registration lags on fertility rates, particularly the total fertility rate (TFR), a comparison of TFRs derived from year of occurrence and year of registration is included below (graph 4.5).