Every 3 years, the Australian Government conducts a developmental census across the entire population of children in their first year of full-time schooling (median age 5 years). The first developmental census was conducted in 2009, including 261,147 children, and in 2012 data were collected on 289,973 children-representing 97.5% and 96.5% of the estimated eligible population, respectively. The questionnaire is completed by teachers on the basis of at least 1 month's knowledge of the child, including aspects of physical, social, emotional, language and cognitive development, as well as data on special needs. Teachers are also asked to include details of the child's care arrangements and attendance in early education programmes in the years preceding school. Demographic and geographical data are recorded at the individual and area levels.