Over the longer term, the rate has decreased by 1.8 percentage points over the last five years and by 5.3 percentage points over the last decade.
Dros y tymor hirach, mae’r gyfradd wedi gostwng 1.8 pwynt canran dros y pum mlynedd diwethaf a 5.3 pwynt canran dros y degawd diwethaf.