Economic activity is estimated from survey data using proportions derived from the Annual Population Survey (APS), which is a household survey carried out by the ONS.
Amcangyfrifir gweithgarwch economaidd o ddata arolwg gan ddefnyddio cyfrannau sy’n deillio o’r Arolwg Blynyddol o’r Boblogaeth, sef arolwg o gartrefi a gynhelir gan ONS.