In cooperation with researchers from the University of Groningen participants' place of birth has been transformed to province of birth. This linkage resulted in a province of birth for X Lifelines participants, which will soon be available for request in the Lifelines catalogue (sections: demographics (nationality & ethnicity) and secondary & linked variables).

Place of birth was obtained from the Personal Records Database Netherlands (basisregistratie personen - BRP). In the first phase of the linkage place of birth was linked to “Woonplaatsen in Nederland” obtained from Statistics Netherlands (CBS) in 2011.

After the first linkage <200 places of birth couldn't be matched and have been matched by hand. Four reasons for a mismatch have been identified

1. Name of municipality instead of place (match generated by researchers University of Groningen)
2. Blanks in name that didn't correspond with linkage file (match generated by researchers University of Groningen)
3. Former name is used (match generated by researchers University of Groningen)
4. Former municipality name is used (match generated by Lifelines)

In two cases no province of birth has been generated:

• Participant was born outside of the Netherlands
• Place of birth was matched to two provinces in the file from Statistics Netherlands