During the year prior to the COVID-19 pandemic, the percentage decreased most months, reaching a low point in December 2019, before increasing in early 2020.
Yn ystod camau cynnar pandemig COVID-19, roedd perfformiad yn erbyn y targed wedi gwella, gan gyrraedd uchafbwynt o 77.9% ym mis Gorffennaf 2020.