This is an increase of 0.1% between 1 December 2020 and 1 December 2021, although a decrease of 0.6% from the peak on 2 March 2020
Mae hyn yn gynnydd o 0.1% rhwng 1 Rhagfyr 2020 ac 1 Rhagfyr 2021, ond yn ostyngiad o 0.6% ers 2 Mawrth 2020