Very careful consideration is given to the questions included in the Census; questions must meet the needs of a substantial number of users in order that it is acceptable to the public and yield good-quality data. The Census is planned and carried out by the Office for National Statistics (for England and Wales), General Register Office for Scotland and the Northern Ireland Statistics and Research Agency. The questions are selected following several rounds of consultation with:
A programme of testing possible questions for the 2001 Census was carried out, including cognitive research into how people understood the questions, small scale quantitative tests and two major Census tests in 1997 and 1999, to ensure that all questions were practical and reliable. In addition, before the final decision on census content was taken by Parliament, the Office for National Statistics (ONS) carried out a sample survey of more than 2000 households as a way of providing a further check on the effectiveness of the questions and the public's view of the topics.