Comparability and coherence: Similar information is available from other parts of the UK but the data is not exactly comparable due to local definitions and standards in each area.
Cymaroldeb a chydlyniad: Mae gwybodaeth debyg ar gael o rannau eraill o’r DU ond nid oes modd cymharu'r data yn llwyr oherwydd safonau a diffiniadau lleol ym mhob ardal.