Over the longer term, the rate has decreased by 3.7 percentage points over the last five years and by 3.5 percentage points over the last decade.
Dros y tymor hirach, mae’r gyfradd wedi gostwng 3.7 pwynt canran dros y pum mlynedd diwethaf, a 3.5 pwynt canran dros y degawd diwethaf.