The coronavirus (COVID-19) pandemic may have impacted on the quality of this data and may have resulted in over recording of this data in 2020 to 2022.
Mae'n bosibl bod pandemig y coronafeirws (COVID-19) wedi effeithio ar ansawdd y data hwn ac efallai ei fod wedi arwain at or-gofnodi'r data hwn yn 2020 i 2022.