A study on the re-identifiability of Dutch citizens

This paper analyses the re-identifiability of Dutch citizens by various demographics. Our analysis is based on registry office data of 2.7 million Dutch citizens, ~16% of the total population. We provide overall statistics on re-identifiability for a range of quasi-identifiers, and present an in-depth analysis of quasi-identifiers found in two de-identified data sets. We found that 67.0% of the sampled population is unambiguously identifiable by date of birth and four-digit postal code alone, and that 99.4% is unambiguously identifiable if date of birth, full postal code and gender are known. Furthermore, two quasi-identifiers we examined from real-life data sets turn out to unambiguously identify a small fraction of the sampled population. As far as we are aware, this is the first re-identifiability assessment of Dutch citizens that uses authoritative registry office data.