The estimates are presented at both a national and regional level, but it is recognised that there will be considerable variation within each region and within each local authority.
Caiff yr amcangyfrifon eu cyflwyno ar lefel genedlaethol a lefel ranbarthol, ond cydnabyddir y bydd cryn amrywiad o fewn pob rhanbarth ac o fewn pob awdurdod lleol.