Some studies also drew on secondary information such as administrative and market research data, or Census, employment and labour market statistics.
Roedd rhai astudiaethau hefyd wedi defnyddio gwybodaeth eilaidd megis data gweinyddol ac ymchwil i’r farchnad, neu ystadegau’r Cyfrifiad ac ystadegau ar gyflogaeth a’r farchnad lafur.