In this paper we attempt to delve into the implications of personal data legislation on Censuses. The primary goal is to highlight the most effective ways to integrate this legislation into the core fabric of the fundamental principles of official statistics that predominantly govern Censuses. For a practical illustration, we utilize the Greek Population and Housing Census of 2021 as a representative example. More specifically, the paper addresses the personal data related issues that arose during the 2021 Census in Greece and the approaches adopted by the Hellenic Statistical Authority (ELSTAT) within the scope of the General Data Protection Regulation (GDPR) of the European Union (EU). The analysis covers a range of aspects that include the particular types of data processed, the specific processing activities across the different phases of the Census and the utilization of data processors. Furthermore, we provide an account of the purposes of use and the legal bases upon which National Statistical Offices (NSOs) can rely on and explore the intricate link between the prevailing conditions under which the Census was deployed and the various data protection considerations that arose. We then elucidate how the Census was built on the 'Privacy by Design' principle and how this approach was crafted taking into account existing operational limitations. Finally, our findings highlight how this strategy not only adhered to but also enhanced best practices that strengthen and complement the fundamental principles of official statistics.
