A self-completion Welsh language use questionnaire was subsequently left for each Welsh speaker between April 2013 and March 2015 to complete and return by post.
Gadewid holiadur Defnydd Iaith i bob siaradwr Cymraeg ei lenwi eu hunain a’i ddychwelyd drwy’r post rhwng Ebrill 2013 a Mawrth 2015.