This proportion decreased by 5.5 percentage points for those aged 17 and by 3.7 percentage points for those aged 18, over the same time period.
I’r rhai 17 oed, gostyngodd y cyfranogiad hwn 5.5 pwynt canran ac i’r rhai 18 oed, gostyngodd 3.7 pwynt canran yn ystod yr un cyfnod.