Congress decides the method used to calculate the apportionment and that method has changed over time. This will be the method used in Census 2000, according to provisions of Title 2, U.S. Code. Since 1930, Illinois has seen its number of House seats decline from 27 to the current 19 as the nation's population has moved south and west. The loss of a seat, combined with a gain in population, means each of Illinois' representatives will now represent approximately 654,000 people. States that gained two seats include Arizona, Florida, Georgia and Texas.
States gaining one seat are California, Colorado, Nevada and North Carolina.
States that lost two seats include New York and Pennsylvania. States losing one seat are Connecticut, Illinois, Indiana, Michigan, Mississippi, Ohio, Oklahoma and Wisconsin. A total of 12 seat changes will take place and involve 18 states. Essentially, Illinois would have had to count more than 152,000 additional residents in the 2000 Census to retain 20 seats in the House of Representatives. Small area population totals that will be used for legislative and congressional redistricting will be available by April 1, 2001.