The statistics were compiled from data collected through the National Early Childhood Education and Care Collection (Collection). The numerator is based on all children who as at 1 July in the collection year were between four and five years of age (inclusive) and were enrolled during the reference period in a preschool program are in-scope of the Collection. To be considered as enrolled, the child must have attended the preschool program for at least one hour during the reference period, or be absent due to illness or extended holiday leave and expected to return.

 The Collection date is the first Friday in August of each year. In an effort to achieve comprehensive coverage, data were sourced from the Australian Government, state and territory education departments and the Catholic Education Office of the Archdiocese of Canberra and Goulburn. Jurisdictions collect and report data for the Collection using a Unit Record Level (URL) collection methodology. This enables the calculation of unique child counts, in estimating the number of children enrolled in a quality early childhood education program. In addition to the data submissions of each jurisdiction, states and territories are also able to provide additional supplementary data in finalising the number of children enrolled in a quality early childhood education program.

The denominator is based on the estimated residential population of four year olds as at June of each year. For more information on ERP see Australian Demographic Statistics (cat. no. 3101.0) and Population by Age and Sex, Regions of Australia (cat. no. 3235.0).