We know from previous censuses that people born outside Wales are much less likely to report being able to speak Welsh than people born in Wales.
Rydym yn gwybod o gyfrifiadau blaenorol bod pobl a gafodd eu geni y tu allan i Gymru yn llai tebygol o lawer o ddweud eu bod yn siarad Cymraeg na phobl a gafodd eu geni yng Nghymru.