This difference is partly explained by socio-economic factors, geographical location and other circumstances, but to an extent the difference remains unexplained (the Welsh Government, 2020b).
Priodolir y gwahaniaeth hwn yn rhannol i ffactorau economaidd-gymdeithasol, lleoliad daearyddol ac amgylchiadau eraill, ond i ryw raddau nid oes esboniad amdano o hyd (Llywodraeth Cymru, 2020b).