In previously published BERD statistics, up to the 2020 reference period, it has been established that there was undercoverage, particularly of small businesses.
Mewn ystadegau BERD a gyhoeddwyd yn flaenorol, hyd at gyfnod cyfeirio 2020, sefydlwyd bod cwmpas anghyflawn, yn enwedig busnesau bach.