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Welsh Demographic Service Dataset (WDSD)

The Welsh Demographic Service Dataset (WDSD), maintained by NWIS, comprises records for all GP registrations in Wales. It includes registration details for all GP practices, including those not signed up to provide clinical information to the databank. It provides a population dataset that can be used as a study denominator. It contains start and end dates for period of GP registration and also for address history, which permits periods of observable time and person time at risk to be estimated.

The WDSD contains a Residential Anonymous Linkage Field (RALF) that identifies a unique address; this field can be used to link records for members of the same household.


All Wales population – approx. 3 million

Data Level

Individual person

Data Years

1990 – Present