The once-a-decade process for redrawing the map of the House of Representatives has two distinct parts with similar-sounding, multisyllabic names. Redistricting, the drawing of the lines within each state, is the second part. Reapportionment, deciding how many House seats each state will have, comes first.
Reapportionment will reflect the results of the 2010 census. As in the past, the South and West have been growing faster than the Northeast and Midwest, so the former regions will gain seats at the expense of the latter. The article explains the mechanics of the process:
The totals provide the raw data for reapportionment based on the “method of equal proportions,” which Congress has used since 1941 to divvy up House seats among the states. The formula is actually used to parcel out only the 385 seats that remain after each of the 50 states is assigned the one seat it is guaranteed under the Constitution.
The rest of the seats are handed out based on statistical “priority values” assigned to each additional seat that a state might get. In as close to plain English as the formula will allow, these priority values are calculated in a two-step process that requires dividing a state’s population by the square root of the product of the number of seats it’s already been assigned and that number plus one. The priority numbers are then rank ordered: “State A” will get an additional seat if its priority value for that seat is greater than any other state’s. The seats are disbursed to states based on these rankings until all 435 have been awarded.
As we discuss in chapter 11, judicial decisions require districts of equal population -- but only within each state. There are substantial differences among states. The article explains:
That each state, no matter how small, is entitled to one seat creates some significant variations from those averages, though. Republican Cynthia M. Lummis , Wyoming’s sole House member, has the smallest constituency; her state’s current population is estimated at 533,000. But another at-large member, Republican Denny Rehberg , has by far the biggest constituency; Montana’s current head count is above 967,000.