[James Bond Agent 007]

Two thoughts:

1. At the Indian tribe I work for, I worked with the Census Bureau last winter and spring to get an accurate address list, and all I can say is, you can add about 5% to those population numbers to get something approximating the "real" number. We got about a 98% response rate, but both during and after the process, it became clear to me there were a lot of addresses that got missed, so the "real" response rate was actually less. I also know people who told me they never got a census form.

2. As someone said above, the timing of the census during (or shortly after) a recession undoubtedly affected the numbers. In particular, lots of immigrants who were here during the boom years of 2004-2007 had gone home and probably account for a lot of the unexpectedly small numbers.