2.1. Population estimates by sex for Australia and each of the States are published quarterly as at 31 March, 30 June, 30 September and 31 December. Estimates by single years of age and sex are compiled quarterly but are only published annually as at 30 June.
2.2. The initial base populations from which subsequent quarterly and annual estimates are derived are provided by the census, and are called census date population estimates. The method used to update these estimates, called the cohort component method, brings forward the population by ageing the base, then adjusting for subsequent births, deaths and overseas and interstate migration.
2.3. Population estimates are referred to as either preliminary, revised or final. Preliminary estimates are generally made available 6 months after the reference period. Revised estimates are generally published each September for the financial year ending in the previous year (eg. revised estimates for the 1997-98 financial year would be available in September 1999). Final estimates are published for the previous intercensal period after each census.