Although personal or attitudinal indicators are important, as data on these are not routinely available at a national level, they are out of scope of this paper.
Er bod dangosyddion personol neu ddangosyddion agwedd yn bwysig, gan nad oes data ar y rhain ar gael fel mater o drefn ar lefel genedlaethol, maent y tu allan i gwmpas y papur hwn.