The Census was held on 27 March 2011, and is a key source of information on the Welsh language. The Office for National Statistics (ONS) is responsible for the Census in Wales and England. The 2011 Census question asked "Can you understand, speak, read or write Welsh"- answered by ticking one or more of five boxes (one for each category and one for "None of these") in any combination. This question was only asked in Wales, and results are presented for those aged 3 and over. The Census did not collect information on fluency levels or on frequency of use.