However, data is missing from some local authorities which can lead to them showing lower cost than in reality, especially Bridgend and Flintshire.
Fodd bynnag, mae data ar goll gan rai awdurdodau lleol, a all arwain atynt yn dangos cost is na'r gwir ffigur, yn enwedig ym Mhen-y-bont ar Ogwr a Sir y Fflint.