The US Census Bureau is required to take a census of population every ten years, during the year ending with zero.According to the Constitution of the United States,this decennial census has one fundamental purpose: to ensure that number of seats each State has inthe U.S. House of Representatives reflects the relative size of the State's population as compared with other States.Currently there are 435 representatives divided among the 50 States. Each of these representatives is elected by the voters of a congressional district,defined as an area established by law for the election of representatives to the U.S. Congress. Each congressional district is to be as equal in population toall other congressional districts in the State as practicable, based on the decennial census counts. The number of congressional districts in each Statemay change after a decennial census. After the number of seats assigned to the individual States is determined (apportionment), the task of drawing thenew congressional districts (redistricting) is generally given to each State legislature. Congressional district boundaries may be changed more than onceduring a decade.(Note 1)
There are also obsolete districts. For example, since the 2000 census, Nebraska has had three districts, but it used tohave as many as six.Over time, the region and demographics represented in a district can change substantially.Furthermore, districts sometimes retain the same boundaries while changing their district numbers.As of the 2000 census the average population per district was 646,946 people. (Note 2)
The above information implies that the US population after the 2000 census was 281,421,510 ( 646,946 people X 435 districts).
The population of the US is estimated to be about 300,000,000 in 2009 and could grow by the time of the 2010 census.Whatever the population will be, it will be divided by the 435 districts to determine the average population per district; this number will be used todetermine how many districts eachstate will have and then each state will determine the size of each of its districts. As populations gow and change,a district may become more representative of one poliitcal party and can determine the electability of the current representative. Some states may loseand some states may gain districts based on their population as a portion of the total US population; a state may become more red or more blue.
The sources for this article are:
Note 1NationalAtlas.gov - Congressional Districts of the US
Note 2Wikipedia - List of United States Congressional Districts