For Wales (and for England), electoral statistics are taken from data supplied to the Office for National Statistics (ONS) by local Electoral Registration Officers.
Ar gyfer Cymru (a Lloegr), cymerir ystadegau etholiadol o ddata a gyflenwir i’r Swyddfa Ystadegau Gwladol (ONS) gan Swyddogion Cofrestru Etholiadol lleol.