Census conducts research on record linkage methods and linkage quality. These unique techniques link two or more files by person and/or address data and un-duplicate files.  The linked files are used for various research and production projects.

The Census Bureau’s Person Identification Validation System (PVS) assigns unique person identifiers to federal, commercial, census, and survey data to facilitate linkages across and within files. The PVS probabilistically matches incoming files to reference files created with data from the Social Security Administration (SSA) Numerical Identification data, and SSA data with addresses obtained from federal files. The Census Bureau conducts ongoing research on the quality of person matches to improve and expand record linkage with a variety of contemporary and historical data sources.