Comparing data across different data collections is essential to advance knowledge. However, such comparisons are highly complex and require careful consideration of data item definitions, age ranges, population groups, time periods and data collection aims. Davenport and colleagues compare the aggregate data we reported for all headspace centre clients from early 2013 with data published from two Sydney centres collected between 2007 and 2009, and with general practice client data from people with self-reported significant mental health problems in 2001. The variance of the Sydney centres demonstrates the diversity among headspace centres, which were rolled out at different time points and responsive to a wide range of community contexts across Australia.1 Consequently, aggregate data provide just one small step in our understanding. With the capability enabled by the new headspace data-collection system implemented in 2013, describing the commonalities and differences between centres and identifying peer groups will be a priority.