Certain sectors are excluded from the sample list (most notably the financial services sector) meaning not all businesses across the economy were invited to participate.
Mae rhai sectorau wedi'u heithrio o'r rhestr enghreifftiol (yn fwyaf arbennig y sector gwasanaethau ariannol) sy'n golygu na wahoddwyd pob busnes ar draws yr economi i gymryd rhan.