Reuben Kendall and Mike Camden

Statistics New Zealand

Confidentiality of longitudinal collections

Longitudinal collections present information from the same ‘reporting units’ over multiple time periods. Such collections are increasing in importance due to their ability to reveal the dynamics of a population: transitions in variables for individuals can be related to transitions in other variables. This contrasts with cross-sectional collections which provide a ‘snapshot’ in time. However, the positive aspects provided by longitudinal data may pose increased risks of disclosure, with information showing transitions over time potentially being highly identifying of individuals.

Longitudinal analysis is relatively new in national statistical agencies. As a result, confidentiality procedures surrounding it are still being investigated and developed. This paper presents a discussion of the risks for providing access to aggregate data and microdata, the current confidentiality measures implemented by national statistical agencies, and the possible solutions for these confidentiality risks.