Whether giving people a number of days to respond to a survey, and by presenting this time period in various ways, leads to greater survey commencement than the traditional ‘due date’ approach.

This was a cluster randomized trial. For this trial, clusters were small statistical areas called mesh blocks that consist of approximately 30 dwellings.

The intervention consisted of two versions of the invitation letter delivered by post. The ABS sends letters to citizens inviting them to participate in a census test.

Primary outcome: proportion of households that commenced the survey prior to October 18 (i.e. up to and including October 17).
Secondary outcome: proportion of households that completed the survey prior to October 18 (i.e. up to and including October 17).

Mesh blocks were stratified by: the difficulty of enumeration in the 2016 census, number of dwellings, enumeration mode in 2016 census (drop-off or mail-out), and mesh block category (residential, primary production etc.). Mesh blocks were selected from strata in groups of four and randomly allocated by computer algorithm to a treatment group on a one-to-one ratio.

Expected sample size: 28,544 households, 892 mesh blocks (approx. 446 per treatment group)