In August 2021 the Office for National Statistics (ONS) recalibrated the weights of Annual Population Survey datasets from January 2020 onwards.
Ym mis Awst 2021 aeth y Swyddfa Ystadegau Gwladol ati i ailgalibradu pwysoliad setiau data’r Arolwg Blynyddol o’r Boblogaeth o fis Ionawr 2020 ymlaen.