Until now, between 1971 and 2006 we had a more complex form of census-taking. Until 1971 everybody got the long form. There was only one census and that was the long form. In 1971 we said the long-form information could be collected from a large sample, one in five, but a sample. Therefore, four in five would get the short form, and one in five would get the long form. The two together were the census.
That's the way it was in 1971, 1976, 1981, 1986, etc., until 2006. In 2011 it will be just a short form. That is now called the census. What used to be part of the census, the long form, is now designated as the national household survey, because that's the only way it can be made voluntary. The object was to make it voluntary and the only legal way to make it voluntary was to separate it from the census and call it a survey.