This proportion decreased by 7.9 percentage points for those aged 17 and by 5.1 percentage points for those aged 18, over the same time period.
I’r rhai 17 oed, gostyngodd y cyfranogiad hwn 7.9 pwynt canran ac i’r rhai 18 oed, gostyngodd 5.1 pwynt canran yn ystod yr un cyfnod.