The gap had previously been relatively stable at around 14.7 percentage points between 2015/16 and 2018/19 before widening in the most recent 3 years.
Roedd y bwlch wedi bod yn gymharol sefydlog o’r blaen, sef tua 14.7 pwynt canran rhwng 2015/16 a 2018/19 cyn ehangu yn y 3 flynedd ddiwethaf.