Data on staff employed by the NHS is available from 1979; however due to changes in the classifications of staff only the overall numbers are strictly comparable over time.
Mae data o 1979 ar gael ar gyfer staff a gyflogir gan y GIG; fodd bynnag, yn sgil newidiadau yng nghategorïau’r staff, dim ond y niferoedd cyffredinol y gellid eu cymharu'n union dros amser.