Apportionment is the process by which representation in legislative bodies is distributed among the people. It may involve the assignment of a number of seats to specified areas, such as states or counties. Each area may then be divided into districts, from which representatives are elected. The reassignment of seats in a legislature among the areas represented is usually called reapportionment. The division of an area into new election districts is called redistricting. However, these terms are often used interchangeably to mean any change in an area’s representation.
Representation has been apportioned in various ways. Two common bases have been (1) population and (2) political units, such as states, counties, or townships. In bicameral (two-house) legislatures, one house may be based on population and the other on political units. For example, in the United States Congress, each state still is allowed two senators regardless of population. States are apportioned seats in the House of Representatives according to population, with each state guaranteed at least one seat. In most states, the state legislature draws up its state’s congressional election districts.
Great differences in the population of districts occur when representation is based on factors other than population. Large differences may arise even when population is the apportionment base. As people move from rural areas to cities and suburbs, some districts become much more heavily populated than others. People in overpopulated districts have less influence in the legislature than do people in underpopulated areas. But legislatures often refuse to redistrict because they wish to protect the seats of some members. In the United States as late as 1962, the population of many state legislative districts varied by as much as 30 to 1.
Initial efforts to get U.S. courts to order redistricting failed. The Supreme Court of the United States held that the issue was of a “political nature” and thus could not be decided by the courts. The Supreme Court reversed this ruling in the 1962 case of Baker v. Carr. In this case, the court held that voters could bring questions of unfair apportionment before federal courts. Since this ruling, legislatures have been undergoing a major redistricting upheaval. Based on 1963 and 1964 rulings, the Supreme Court developed the “one-person, one-vote” principle. As a result, all congressional districts must be “substantially equal” in population, and districts for electing both houses of state legislatures must meet the same requirement. The principle was extended to local governments in 1968. In 1969, the court demanded that the states try to make their congressional districts precisely equal in population. In 1973, the court clarified its position on state legislative districts. It ruled that the populations of these districts need not be exactly equal if the districts were drawn to reflect legitimate considerations, such as following political subdivisions or equalizing political opportunity.
