You can pay anything from # 250 to # 600 plus for different surveys, which differ in detail. (idealhome.co.uk)
Direct respondents to take different surveys based on location, demographic, or other criteria - all using the same link. (qualtrics.com)
The following chart displays the results and highlights the differences between the 1994 survey results and those collected in 2010 (albeit, with slightly different survey methods). (sciencedaily.com)