The sector exclusions were decided in-line with the measurement of trade for national accounts as well as seeking to harmonise exclusions made by other, similar, surveys.
Penderfynwyd gwaharddiadau'r sector yn unol â mesurau masnach ar gyfer cyfrifon cenedlaethol yn ogystal â cheisio cysoni gwaharddiadau a wnaed gan arolygon tebyg eraill.