EFFECTS ON FERTILITY RATES

Total fertility rates (TFRs) represent the average number of babies that a woman could expect to bear during her reproductive lifetime, assuming current age-specific fertility rates were experienced. As the delay of birth registrations may be greater than a year, year of occurrence data for recent years are likely to be affected by lags in registration, particularly for births to Aboriginal and Torres Strait Islander women, therefore TFRs are presented up to and including 2007 only. In addition, TFRs have been calculated on a state of usual residence basis, as there is no available denominator to calculate rates based on a state of registration.

In Australia, TFRs calculated using registration and occurrence data have followed similar trends in the past decade. The divergence between 2002 and 2004 was largely due to registration lags in New South Wales. These delays were reduced through the implementation of improved follow-up procedures in 2005. See table 4.13 for state and territory TFRs calculated using registration and occurrence data.

In Queensland, TFRs based on the year of registration compared with those based on the year of birth (occurrence) show the effect that delayed birth registrations may have. In particular, for 2005 and 2006, TFRs based on year of registration (as published in this publication) were lower than those based on the year of occurrence of the birth, indicating that fertility rates may have been underestimated over this period.

Conversely, in 2007, the TFR for Queensland based on year of registration was higher than that based on the year of occurrence. This indicates a possible overestimation of fertility rates due to the registration of births that occurred in earlier years.

For 2007, all states and territories, except for New South Wales, recorded higher TFRs based on year of registration than those based on year of birth, with Queensland recording the largest difference.

Fertility rates of Indigenous women

Due to delays in the registration of births to Aboriginal and Torres Strait Islander women, TFRs for Aboriginal and Torres Strait Islander women were higher using year of occurrence data compared with year of registration data. This is true for all states and territories, except the Northern Territory where TFRs on both bases follow a similar trend. This reflects the short registration lag (1.4 months in 2007) for Aboriginal and Torres Strait Islander births registered in the Northern Territory.

In the late 1990s, TFRs for Australia based on year of registration may have been underestimated as more births occurred than were registered in these years. Conversely, since 2002, TFRs based on year of registration may have overestimated the fertility rate as the Registrars register previously unregistered births that occurred in earlier years.

Prior to 2007, the TFR for Aboriginal and Torres Strait Islander women in Queensland was higher when based on year of occurrence data than when based on year of registration, indicating that delays in the registration of births may have led to an underestimation of fertility rates (as reported in this publication). For 2007, there was an increase in the TFR based on registered births relative to the TFR based on births by year of occurrence.

For 2007, all states and territories recorded higher TFRs of Aboriginal and Torres Strait Islander women based on year of registration than those based on year of birth. Queensland recorded the largest difference and the Northern Territory recorded the smallest difference, reflecting the difference in the length of registration lag. The differences are larger than those for all women due to the longer delays in registrations for births registered to Aboriginal and Torres Strait Islander women. Therefore, TFRs for Aboriginal and Torres Strait Islander women based on year of registration should be interpreted with caution as data may not accurately reflect the level of Aboriginal and Torres Strait Islander fertility for any particular year.

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