VOA常速英语:308,529,148....Give or Take a Few

Very shortly, the decennial - meaning every-10th-year - census of the nation's population, which is mandated by the U.S. Constitution, will get underway.

And there's a lot more to it than just trying to count the number of Americans. The population keeps moving around, so after each head count some states gain - and others lose - members in the U.S. House of Representatives, where the number of seats is based on each state's official population. Data gathered from census surveys mailed to American households - and reported by Census workers sent out to find those who do not respond - also helps decide where billions of federal dollars get spent on new schools, highways and health care.

So you'd think every citizen would want to be sure to be counted. But no.  As in every census, some people just don't reply and illegal immigrants mostly avoid census-takers. In a recent nationwide poll by the Pew Research Center, 12 percent of Americans said they weren't sure they'd cooperate with the census effort and 6 percent said they probably or certainly would not.

The bureau dropped the sampling idea. When it came up again for 2010, sampling was shouted down.  

And last year, the Obama White House announced that senior administration appointees would work closely with the Census Bureau in supervising the 2010 Census. Republicans called it unconstitutional and a power grab.

So it looks like what is supposed to be a simple enumeration - or careful count - of the nation's population this year will be anything but routine.