It should be noted, however, that the National Census and Annual Population Survey use different sampling methods and are not therefore directly comparable.
Dylid nodi, fodd bynnag, fod y Cyfrifiad Cenedlaethol a'r Arolwg Blynyddol o'r Boblogaeth yn defnyddio gwahanol ddulliau samplu ac felly nad oes modd eu cymharu'n uniongyrchol.