The census is performed because the Constitution requires it. It would be clearly unconstitutional to not perform one every ten years, sort of like saying the president could stay in office indefinitely.
The Census is just a count of the population; in theory, it is an accurate count of who lives where on April 1 of the Census year. Obviously, it’s not perfect, so people are missed. However, the constitution makes it clear the representation is determined by the Census and by nothing else, so it needs to be done as best it can be done.
Other questions are part of a confirmation (in the early days, the Census was the only way to get any income information, but things have changed). The census numbers, because they’re an actual count, are considered more accurate than the various estimates, which is why it is used by other programs as a basis for calculating how funds are paid.
The Census Bureau isn’t hoping to “catch” anyone. Illegal aliens are counted, but are not turned over to authorities or reported in any way. However, knowing the number of illegal aliens is important in planning; they aren’t going to vanish, and some may end up becoming legal some day. Further, Census data is kept sealed for a very long time; by the time anyone could look at it, most of the people involved are dead (I think they’ve released up to the 1920 Census).
There’s no doubt that the Census undercounts, especially in inner cities. But as far as determining representitives is concerned, it is the only legal way. There’s been some talk about sampling to mathematically reduce the error, but it seems quite likely that using sampling to determine representation would be unconstitutional. (Using it to determine funding probably isn’t; the Census has always been used because it was accurate enough and relatively nonpartisan, but there’s no requirement the actual census numbers be used – though it would be a major fight to get sampling accepted even here.)
Finally, the system *is[/is] automated. The computer card was developed around 1880, in part to perform the census (I think it was the 1870 Census that took over ten years to compile). Up until at least 1950 (and probably later) all census takers went door to door on April 1. The mail census was a major automation improvement.
“What we have here is failure to communicate.” – Strother Martin, anticipating the Internet.
www.sff.net/people/rothman