As well as year to year comparisons it is recommended to compare the most recent data with data from 2018-19, which was the last year before the start of the pandemic.
Yn ogystal â chymharu data o flwyddyn i flwyddyn, mae’n cael ei argymell i gymharu'r data mwyaf diweddar gyda data o 2018-19, sef y flwyddyn olaf cyn i’r pandemig cychwyn.