There was an upward trend from 2018 to 2020, rates were stable in 2020 and 2021, there was slight reduction in 2022, and a slight increase again in 2023.
Roedd tuedd ar i fyny rhwng 2018 a 2020, roedd cyfraddau'n sefydlog yn 2020 a 2021, bu gostyngiad bach yn 2022, a chynnydd bach eto yn 2023.