Measuring Hard-to-reach Groups in Administrative Sources

Providing guidance to national statistical bodies, the document outlines methods to harness administrative data for capturing elusive groups like the homeless, undocumented migrants, immigrants, and emigrants. It clarifies both the capabilities and limitations of these sources in crafting official statistics.
The document aims to support experts working in national statistical offices and other agencies producing official statistics in using data from administrative sources for measuring hard-to-reach groups, namely the homeless, undocumented migrants, immigrants and emigrants. The document also helps data users understand the potential and limitations of administrative sources for producing official statistics on these groups. The document was endorsed by the Conference of European Statisticians at its 2025 plenary session in June 2025.

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