In May 2020, due to the COVID-19 pandemic the National Survey changed mode from a face-to-face interview to one over the telephone.
Cafodd cyfweliadau wyneb-yn-wyneb eu hatal ym mis Mawrth 2020 yn sgil pandemig y coronafeirws (COVID-19), a chynhaliwyd yr holl gyfweliadau dros y ffôn.