A number of methodological improvements for BERD and HERD, as well as regular revisions to the survey data because of further validation, have been implemented for the 2018 period onwards.
Mae nifer o welliannau methodolegol ar gyfer BERD a HERD, yn ogystal â diwygiadau rheolaidd i ddata'r arolwg oherwydd dilysu pellach, wedi'u gweithredu ar gyfer y cyfnod o 2018 ymlaen.