This work was commissioned to investigate whether the new survey would produce different results, and so to provide information on what the change means for understanding trends over time.
Bydd y prosiect yn darparu adolygiad a chrynodeb o'r datblygiadau hyn er mwyn deall effeithiau modd neu ddylunio ar y broses o gasglu data, gan nodi os oes angen gwaith ymchwil pellach.