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Apportionment is the distribution of legislative seats among pre-existing territorial or other units entitled to representation. Although apportionment, districting, and electoral methods are interrelated, the problems involved in one are quite different from those involved in either of the other two. Districting establishes the precise geographic boundaries of a territorial constituency. The electoral system prescribes the method for electing representatives. United States constitutional practice distinguishes between apportionment and districting by vesting the two functions in different governments. The national government apportions representatives to the 50 states, but the state governments divide their respective states into congressional districts. In the United Kingdom, on the other hand, seats in the House of Commons are distributed merely by dividing the country into constituencies with special boundaries and with a relatively equal number of voters in each constituency.

History. The historical development of apportionment can be seen in the evolution of popular representation in the British House of Commons. The assignment of two members to each county and borough did not seriously violate the popular principle when the population was rather evenly distributed among these units. With the industrial revolution, however, came great shifts in the distribution of population. Many new centers of population, like Birmingham and Manchester, were either completely unrepresented or grossly under-represented while rotten boroughs, like Old Sarum with only seven inhabitants, sent two members to the House of Commons.

Although the Reform Act of 1832 was not based on the democratic principle of apportionment according to population, 42 new parliamentary boroughs were created to provide representation for the new centers of population, the less populous boroughs were apportioned only one member rather than two, and the 56 least populous boroughs were abolished as separate parliamentary constituencies. The seats were redistributed again in 1867. The Redistribution Act of 1885 adopted the principle of the single-member constituency but allowed 27 constituencies to elect two members each. Similarly, community representation yielded to districting based on population, although only a rough arithmetic equality was achieved. A fourth redistribution act was passed in 1918 and a fifth in 1944. This last act—with amendments adopted in 1945, 1947, and 1948—abolished the multi-member constituency, approached arithmetic equality with approximately 56,000 voters in each constituency, and established four separate boundary commissions (England, Wales and Monmouth, Scotland, and Northern Ireland). As a result of the recommendations made by these commissions, the Representation of the People Act of 1948 completely redrew the boundaries of the constituencies. Thus, the acts of 1832 and 1867 were apportionment measures, but the acts of 1885, 1918, and 1944 involved both apportionment and districting, and the act of 1948 involved only districting.

The units to which representation is apportioned are usually territorial subdivisions, such as regions, provinces, states, counties, or a similar geographic unit. Canadian senators, for example, are apportioned to the five senatorial regions, members of the Canadian House of Commons to provinces, Mexican congressmen to states, and the seats in most state legislatures in the United States to countries. Representation may be apportioned, however, to functional groupings of the population. In the early parliaments of Europe, representation was apportioned to social estates (e.g., nobility, clergy, and commons). Theoretically, 70 per cent of the seats in the Cyprian House of Representatives are apportioned to the Greek community and 30 per cent to the Turkish. Similarly, representation in the Spanish Cortes and in the Portuguese Corporative Chamber is apportioned to industrial, labor, cultural, and professional associations.

Basis of apportionment. The basis of apportionment is often confused with the units to which representation is apportioned. Because representation is usually apportioned to territorial subdivisions, the literature on apportionment frequently describes two bases of representation: area and population. The territorial extent of certain sparsely populated constituencies has sometimes been offered as an excuse for establishing some districts that are less populous than others. Except for an abortive attempt in Wisconsin in 1952, actual practice in Illinois in 1955, and recent proposals in Michigan and Nebraska in 1962, no responsible group has ever seriously advocated apportionment of representation on the basis of acres, square kilometers, or any other such territorial measure. In apportionment “area” simply refers to the distribution of representation among territorial subdivisions with previously defined boundaries. In districting “area” refers to the consideration given not only to population equality but also to topography, to the boundaries of civil subdivisions, to the means of travel and communication, and to community of social, political, and economic interest.

Whereas most political scientists would give consideration to these “area” factors in districting, virtually all political scientists agree that population is the only legitimate basis for apportionment in a democratic state. They are not agreed, however, on a definition of population. If actual voters bear a constant relation to total inhabitants, citizens, and registered electors in every unit entitled to representation, it is inconsequential which of these four measures of population is used as the apportionment base. If such a uniform relation is not present, however, apportionment on any basis other than actual voters frequently will not achieve the democratic ideal of an equal ballot for every voter. In 1962, for example, representatives were apportioned to New York and Louisiana almost exactly according to total population, but one popular vote cast for a representative in Louisiana had approximately 81/2 times the weight of one cast in New York—because the number of voters per 100 inhabitants was 33 in New York but only 3.8 in Louisiana.

Apportionment patterns. Four apportionment patterns are common today.

(1) On the basis of population. Deputies in the Soviet Union, for example, are apportioned to each electoral area on the basis of one deputy for every 300,000 inhabitants, so that the total number of deputies is flexible since the ratio is fixed at 1:300,000. Most legislative bodies, however, have a fixed number of seats and a flexible ratio. Older methods for apportioning a fixed number of seats used a ratio, which was determined by dividing the total representative population by the total number of seats. The total representative population of each unit entitled to representation was then divided by the ratio to determine the number of seats to be apportioned to that unit. This method was used for apportioning United States representatives before 1911 and is still widely used for apportioning seats in American state legislatures among the several counties. Apportioning according to a ratio is not sound mathematically if the total number of seats is fixed. Mathematically sound methods assign one seat to each unit and then apportion the remaining seats among the several units according to priority numbers, which may be computed in one of five ways—smallest divisors, harmonic mean, equal proportions, major fractions, or greatest divisors—each of which is designed to apportion seats precisely according to population (Silva 1962). The major-fractions formula was used for apportioning United States representatives to the states in 1911 and 1931, whereas the equal-proportions formula was used in 1941, 1951, and 1961.

(2) On the basis of population but with weighted ratios. The Soviet constitution of 1924, for example, apportioned seats in the All Union Congress to urban areas on the basis of one deputy per 25,000 electors, but to rural areas on the basis of one deputy per 125,000 inhabitants; thus, the urban areas were probably overrepresented in relation to the rural areas. Conversely, many states in the United States apportion seats in their respective legislatures to the less populous counties on the basis of a ratio smaller than that used for apportioning seats to the more populous counties, so that a ballot cast in a less populous county has greater weight than one cast in a more populous county.

(3) On the basis of population but with separate representation guaranteed to the least populous units and/or with a limitation on the representation of the most populous units. In the Fifth Republic, for example, 255 French senators are apportioned among the 90 departments of Metropolitan France roughly according to population, but each department is guaranteed 1 senator and no department has more than 22. The guarantee of separate representation to the least populous units severely limits the popular principle if the population is not rather evenly distributed among the units and if the total number of units is high in relation to the total number of seats. Until the system was invalidated by the courts, each of the 105 counties in Kansas, for example, was guaranteed 1 seat in the Kansas House, so that only 20 seats were left to be apportioned according to population. As a result, the 4 most populous countries with over 37 per cent of the state’s population had only 12 per cent of the seats in the Kansas House. Such a chamber could be made more representative only by greatly increasing the number of seats, by reducing the number of counties, or by joining two or more of the less populous counties into one constituency.

(4) On the basis of equal representation for each subordinate governmental unit regardless of population. Various federal states—for example, Australia, Brazil, Canada, the Federal Republic of Germany, Nigeria, and the United States of America—have a bicameral federal system; one chamber is apportioned on the basis of population, whereas in the other chamber the constituent governmental units enjoy equal (or nearly equal) representation with no (or little) regard for population statistics.

Criteria for apportionment and districting. The two criteria for measuring the equity of an apportionment are: (1) the number of representative inhabitants per seat, which results from dividing a unit’s representative population by that unit’s number of seats (A/a), and (2) the individual representative inhabitant’s share of one seat, which results from dividing his unit’s number of seats by his unit’s representative population (a/A). When the total number of seats is fixed, an apportionment is mathematically satisfactory if the discrepancy between the number of inhabitants per seat in any two units (A/a and B/b) and the discrepancy between an individual inhabitant’s share of one seat (a/A and b/B) cannot be reduced by apportioning one more seat to unit A and one less to unit B, or vice versa. Of the five modern apportionment methods, only equal proportions can be proved to meet both tests, i.e., to minimize the differences in the number of inhabitants per seat and to minimize the differences in each inhabitant’s share of one seat. In practice, however, major fractions and equal proportions will almost always produce precisely the same distribution of seats.

The criteria for districting are much less precise. It is generally agreed that each constituency should be composed of contiguous and compact territory and should contain, as nearly as practicable, an equal number of representative inhabitants. Although the meaning of contiguity is relatively obvious, there is no standard measure of compactness. Nor is there any consensus on the permissible size of population differentials between constituencies. It is also agreed that representation should be based on community of interest, but no serious efforts have been made to draw the boundaries of constituencies scientifically by employing methods of area and demographic analysis, which social scientists have used successfully in determining marketing, shopping, and service districts. The imprecision of the criteria for districting has made “gerrymandering”—i.e., the creation of artificial constituencies with arbitrary boundaries that are consciously drawn for partisan advantage—a serious and unsolved problem in the United States.

The question of the multimember versus the single-member constituency is meaningless except in relation to the electoral system to be used in that constituency. The discrepancy between a political party’s share of the total popular vote and its share of the seats in the chamber, the possibility of gerrymandering, and the number and alignment of political parties depend quite as much on the electoral system as on the number of representatives to be elected in the constituency. Allowing representation for a minority party in a constituency requires both a multimember constituency and a proportional or semiproportional electoral system so that a constituency’s seats can be divided between two or more parties. The apportionment of more than three seats to a constituency with such an electoral system tends to promote a splintering and multiplication of parties. The more seats apportioned to a constituency with such an electoral system, the more precise is the proportionality between each party’s share of the vote and its share of the seats, but this proportionality increases at a decreasing rate as the number of seats per constituency increases. With a block electoral system, however, a corresponding disproportionality increases at an increasing rate.

Where a block electoral system and the single-member or two-member constituency have prevailed, the drive for “fair representation” has been concerned largely with apportionment and districting. In other countries, however, apportionment of the popular house has generally been, at least roughly, according to population, districting has been irrelevant, and attention has been focused on devising an electoral system that would give (or prevent giving) parliamentary representation with arithmetic precision to the various minority parties found in each multimember constituency.

Ruth C. Silva

[See alsoElections; Legislation; Representation.]


Alker, Hayward R. JR.; and Russett, Bruce M. 1964 On Measuring Inequality. Behavioral Science 9:207–218.

Butler, David 1955 The Redistribution of Seats. Public Administration 33:125–147.

Canada, Parliament, House OF Commons 1958 British North America Act. Volume 2, pages 1088–1104 in Debates. Session 1. Ottawa (Canada).

de Grazia, Alfred 1951 Public and Republic: Political Representation in America. New York: Knopf.

Everett, Robinson O. (editor) 1962 The Electoral Process: Part II. Law and Contemporary Problems 27:327–433.

Griffith, Elmer C. 1907 The Rise and Development of the Gerrymander. Chicago: Scott, Foresman.

Kramer, Robert (editor) 1952 Legislative Reapportionment. Law and Contemporary Problems 17:253–469.

Nagel, Stuart S. 1965 Simplified Bipartisan Computer Redistricting. Stanford Law Review 17:863–899.

Peaslee, Amos Jenkins (editor) (1950) 1956 Constitutions of Nations. 3 vols., 2d ed. The Hague: Nijhoff.

Schattschneider, E. E. et al. 1962 A Symposium on Baker v. Carr. Yale Law Journal 72:7–106.

Schmeckebier, Laurence F. 1941 Congressional Apportionment. Institute for Government Research of the Brookings Institution, Studies in Administration, No. 40. Washington: The Institute.

Silva, Ruth C. 1962a Apportionment in New York. Part 1: The Legal Aspects of Reapportionment and Redistricting; Baker v. Carr. Fordham Law Review 30: 581–595.

Silva, Ruth C. 1962b Apportionment of the New York Assembly. Fordham Law Review 31:1–72.

Silva, Ruth C. 1964 Compared Values of the Single-and the Multi-member Legislative District. Western Political Quarterly 17:504–516.

Silva, Ruth C. 1964 Relation of Representation and the Party System to the Number of Seats Apportioned to a Legislative District. Western Political Quarterly 17:742–769.

Weaver, James B.; and Hess, Sidney W. 1963 A Procedure for Nonpartisan Districting: Development of Computer Techniques. Yale Law Journal 73:288–308.

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The process by which legislative seats are distributed among units entitled to representation; determination of the number of representatives that a state, county, or other subdivision may send to a legislative body. The U.S. Constitution provides for a census every ten years, on the basis of which Congress apportions representatives according to population; each state, however, must have at least one representative. Districting is the establishment of the precise geographical boundaries of each such unit or constituency. Apportionment by state statute that denies the rule ofone-person, one-voteis violative ofequal protection of laws.

Also, the allocation of a charge or cost such as real estate taxes between two parties, often in the same ratio as the respective times that the parties are in possession or ownership of property during the fiscal period for which the charge is made or assessed.

Who are to be the electors of the Federal Representatives? Not the rich more than the poor; not the learned more than the ignorant; not the haughty heirs of distinguished names, more than the humble sons of obscurity and unpropitious fortune. The electors are to be the great body of the people of the United States (james madison, The Federalist No. 57).

The difference most relied upon, between American and other republics, consists in the principle of representation (James Madison, The Federalist No. 63).

James Madison and his fellow founders of the United States of America sought many objectives as they framed the U.S. Constitution. Among the goals these champions of democracy fought for was the notion of equal representation in government, by congresspeople, for citizens of the United States. To ensure that equal representation occurred, the founders proposed that the U.S. population be counted at regular intervals with a census. They later agreed, in the Great Compromise of 1787, that congressional representation should be assigned—in other words, apportioned—to various regions of the country based on a total population standard.

Both Article 1, Section 2, Clause 3, and Amendment 14, Section 2, of the Constitution provide that representatives shall be apportioned among the states according to their respective numbers and that a population count will be taken by census every ten years. Apportionment requires that each state's total population be divided by the population of "the ideal district" to determine the appropriate number of representatives. The population of an ideal district, for purposes of federal apportionment, is defined as the total population of the state (as determined by census) divided by one hundred (for the House of Representatives), or by 50 (for the Senate).

In the centuries that followed the United States's adoption of the Constitution, apportionment for the federal Congress has been based on total population—with the exception that a slave, until the Civil War, was considered property and thus counted only as three-fifths of a white person. Efforts to limit federal congressional apportionment to only people who are citizens or voters have been defeated, because the exclusion of groups such as illegal aliens, nonvoters, and children could significantly affect some areas of the country, since some states have large populations of these groups. Shifting political power away from an area means fewer legislators to demand a fair share of government resources for that area.

One such effort to exclude these groups, which occurred during the 1866 debates over the passage of the fourteenth amendment, ultimately led to Congress's voting to continue basing apportionment on total population and to count the "whole number of persons in each state." In contrast, state legislatures have only been required to be based substantially on population since 1964 (reynolds v. sims, 377 U.S. 533, 84 S. Ct. 1362, 12 L. Ed. 2d 506). In 1968, the U.S. Supreme Court extended this requirement to municipal governments as well (Avery v. Midland County, 390 U.S. 474, 88 S. Ct. 1114, 20L. Ed. 2d 45).

Apportionment is related to, but is not the same as, the electoral system and the districting process: apportionment is the manner in which representation is distributed; the electoral system is the way an individual representative is elected; and the districting process establishes the precise electoral boundaries of a representative's district. Apportionment for the U.S. Congress, which consists of the Senate and the House of Representatives, has always been determined by the Constitution. Each state is assigned two senators, who were originally elected by state legislatures but since the adoption of the seventeenth amendment in 1913 have been chosen by direct voter election.

Membership in the House of Representatives is also assigned to the states and is apportioned according to population, with each state being constitutionally guaranteed at least one representative. The House of Representatives grew proportionally with the population of the United States until 1912, when the House froze its size at 435 members. Since 1941, the census bureau has used the system of equal proportions to determine how many of the 435 representatives each state is entitled to have. This

method, developed in 1920 by Professor Edward V. Huntington, of Harvard University, establishes the smallest possible difference between the representation of any two states, since a state's fair share of representatives will rarely be a whole number. The 1941 federal statute 2U.S.C.A. §§ 2a and 2b provides that

under the equal proportions method, the priority list of states or counties among which Representatives in excess of one per state or county are to be allocated is obtained by dividing the population of each state or county by the geometric mean of successive numbers of Representatives.

Congress must decide how to treat the fractional components whenever it reapportions congressional seats based on new census data. This decision affects the distribution of only a few seats in Congress and the electoral college, but in closely contested matters, such as the presidential election of 1876, those seats could mean the difference between victory and defeat. (The electoral college is the body of electors of each state chosen to elect the president and vice president. Apportionment affects the electoral college because it influences the number of electoral votes coming from various areas of the country.) Each state legislature is responsible for establishing the district boundaries of the congressional seats apportioned to the state by the federal government.

From 1842 to 1911, Congress required that all congressional districts be of compact and connecting territory. That stipulation was not continued after 1912, and by the 1960s, the districts within some states differed greatly in size. These disparities were caused in some cases by gerrymandering, which is the process of drawing boundaries for election districts so as to give one party a greater political advantage. Large disparities led a group of urban Tennessee voters to bring suit against their state's electoral commission on the ground that the apportionment of the legislature was unfair. The Supreme Court's March 1962 decision in favor of the voters in baker v. carr, 369 U.S. 186, 82 S. Ct. 691, 7 L. Ed. 2d 663, established the rule that a citizen may bring suit against legislative malapportionment when it deprives that citizen of equal protection under the law as guaranteed by the Fourteenth Amendment. Previously, in Cole-grove v. Green, 328 U.S. 549, 66 S. Ct. 1198, 90 L. Ed. 1432 (1946), the Court had refused to accept jurisdiction in apportionment cases.

Although the Supreme Court's decision in Baker was limited, it did rule that if a system other than one based on population is used for apportionment, the resulting districts must not be arbitrary or irrational in nature. In 1964, the Supreme Court extended Baker by ruling in Wesberry v. Sanders, 376 U.S. 1, 84 S. Ct. 526, 11L. Ed. 2d 481, that legislative districts for the House of Representatives must be drawn so as to provide "equal representation for equal numbers of people," a concept often referred to as the one-person, one-vote standard. Later that same year, in lawsuits directly involving 15 states, the Supreme Court ruled in Reynolds v. Sims, 377U.S. 533, 84 S. Ct. 1362, 12 L. Ed. 2d 506, that districts for state legislatures must also be substantially equal in population. Further extending the principle, the Court ruled in Avery v. Midland County, 390 U.S. 474, 88 S. Ct. 1114, 20 L. Ed. 2d 45 (1968), that if county, city, and town governments elect their representatives from individual districts, the districts must be substantially equal in population.

Other individuals and states have subsequently challenged the method of apportionment used in the United States when that method has proved unfavorable for them. For example, in Franklin v. Massachusetts, 505 U.S. 788, 112 S. Ct. 2767, 120 L. Ed. 2d 636 (1992), Massachusetts and two of its registered voters filed an action against Secretary of Commerce Barbara B. Franklin, alleging, among other things, that the decision to allocate overseas employees was inconsistent with the Constitution. In June 1992, the Court reversed a federal district court decision in favor of Massachusetts, ruling that the allocation of overseas federal employees to their designated home states was consistent with the usual-residence standard used in early censuses and served the purpose of making representation in Congress more equal.

The state of Montana sued the U.S. commerce department, following the 1990 census, when it and 11 other states each lost one House seat. In seeking to keep the two seats it had held since 1910, Montana argued that the method of equal proportions was unconstitutional because it left the state with a single congressional district of 803,655 people—a number almost 40 percent larger than "ideal district size," which is a national average of 572,466 people. Montana also alleged that the variance between the single district's population and that of an ideal district could not be justified under the one-person, one-vote standard developed in Wesberry. The Montana case was appealed to the U.S. Supreme Court, which in March 1992 unanimously upheld the method Congress uses to reallocate congressional seats among the states after a census (United States Department of Commerce v. Montana, 503 U.S. 442, 112 S. Ct. 1415, 118 L. Ed. 2d 87).

The political impact of the census on congressional apportionment was made apparent when the Commerce Department proposed that statistical sampling be used for the 2000 census. (Statistical sampling is a method of surveying a subset of a larger population and applying the findings to the larger group.) Republicans in Congress reacted hostilely to this proposal from the Democratic administration of President bill clinton, fearing that the proposed statistical sampling of hard-to-count persons (racial and ethnic minorities, poor persons, children, illegal aliens, renters, etc.) would favor large urban areas that were aligned with the democratic party. Members of Congress filed suit to block the use of sampling and the Supreme Court agreed with their position in Commerce Dept. v. U.S. House of Representatives, 525 U.S. 316, 119 S.Ct.765, 142 L. Ed. 2d 797 (1999). The Court held that the Census Act, which was first enacted in 1954 (and amended a number of times since then), expressly prohibited the use of sampling to determine populations for congressional apportionment purposes.

This ruling did not end the controversy over what constituted sampling. Following the 2000 census, the state of Utah filed suit against the Commerce Department, alleging that it should have increased its congressional representation from three seats to four. According to the census, the state had achieved a dramatic 30 percent population growth in ten years. Despite this growth, the number of representatives in the state did not increase. North Carolina, however, did pick up an additional seat through a statistical method called imputation. This method permits the Census Bureau to impute, or estimate, the number of members in a household after census takers make repeated efforts to make direct contact. Comparing the numbers of imputed residents of Utah and North Carolina, Utah realized that if it could have these numbers thrown out by a federal court, the North Carolina seat would shift to Utah.

A three-judge panel rejected Utah's arguments that imputed numbers amounted to statistical sampling as prohibited by the 1999 Supreme Court decision. The panel concluded that it was common sense to realize that census takers would not be able to count every person and that reasonable alternatives needed to be employed to fill in the missing numbers. The actual enumeration required by the Census Clause did not mean that the court should reduce the number of persons imputed to households to zero. The imputation method was on the whole fair because it was adjusted for local neighborhood demographics and it was employed only after census takers failed on repeated attempts to contact the households in question. Therefore, the panel ruled that reducing the number to zero would be "inconsistent with the constitutional imperative of actual enumeration," for actual residents would not be counted.

In Utah v. Evans, 536 U.S. 452, 122 S. Ct. 2191, 153 L. Ed. 2d 453 (2002), the Supreme Court affirmed the lower court ruling. The Court, in a 5–4 decision, rejected the idea that actual enumeration under the Census Clause was intended as a description of the only methodology for counting U.S. citizens. The Court pointed out that an interest in accuracy was favored by the Census Bureau, which used imputation as a last resort only after other methods had failed The majority also decided that this method, used as a last resort, was not the same as sampling. Justice stephen breyer noted that "sampling seeks to extrapolate the features of a large population from a small one, but the Bureau's imputation process sought simply to fill in missing data as part of an effort to count individuals one by one." Moreover, the imputation method was not the equivalent of statistical sampling because the two methods were viewed as distinctly different when an amendment to the Census Act was passed in 1958.

further readings

"'Advice' from the Very Beginning, 'Consent' When the End Is Achieved." 1989. American Journal of International Law 83 (October).

Corpus Juris Secundum United States, vol. 91, secs. 11–12.

Cox, Gary W., and Jonathan N. Katz. 2002. Elbridge Gerry's Salamander: The Electoral Consequences of the Reapportionment Revolution. New York: Cambridge Univ. Press.

"Fair Representation: Meeting the Ideal of One Man, One Vote." 1984. Michigan Law Review 82 (February).

The Federalist Nos. 37, 38, 52, 54, 56, 57, 58, 62, and 63. 1787–88.

"A House of Our Own or a House We've Outgrown? An Argument for Increasing the Size of the House of Representatives." Columbia Journal of Law and Social Problems 25.

"Lies, Damn Lies and Statistics: Dispelling Some Myths Surrounding the United States Census." 1990. Detroit College of Law Review 1990 (spring).

"Montana's Lost Seats Begs Issue." 1992. National Law Journal (March 2).

"Politics and Purpose: Hide and Seek in the Gerrymandering Thicket after Davis v. Bandmer." 1987. University of Pennsylvania Law Review 136 (November).

"Reapportionment: The Supreme Court Searches for Standards." 1989. Urban Law 21 (fall).

Scher, Richard K. 1996. Voting Rights and Democracy: The Law and Politics of Districting. San Francisco: Wadsworth.

"The Thickest Thicket: Partisan Gerrymandering and Judicial Regulation of Politics." 1987. Columbia Law Review 87 (November).

"Understanding Dworkin." 1993. George Mason Independent Law Review 1 (spring).

Yarbrough, Tinsley E. 2002. Race and Redistricting: The Shaw-Cromartie Cases. Lawrence: Univ. Press of Kansas.


Congress of the United States; Voting.

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APPORTIONMENT is the decennial computation and assignment of seats in the House of Representatives to the individual states, or the allocation of legislative seats within a state. Article I, section 2, clause 3, of the U.S. Constitution as amended by the Fourteenth Amendment provides for the apportionment of seats in the U.S. House of Representatives every ten years on the basis of population, except for the rule that each state shall have at least one representative. However, this constitutional provision is silent on how the congressmen are to be elected. To remedy the common practice of at-large or "winner take all" elections, the Apportionment Act of 1842 required single-member congressional districts, composed of contiguous, or adjoining, territory. In 1872 Congress legislated that all districts should contain "as nearly as practicable an equal number of inhabitants," and in 1901 it passed a law requiring that districts should be of "compact territory."

Technically speaking, Congress apportions its House membership, and the states district themselves for the election of representatives. After the 1920 census, which showed for the first time that urban Americans outnumbered rural Americans, Congress was deadlocked on how to reapportion its House seats. To avoid future impasses, Congress in 1929 provided for a so-called permanent system of reapportionment that would discourage further growth in the size of the House and would obviate the necessity for further congressional action on the subject. Unfortunately, the 1929 reapportionment act did not specify that districts were to be contiguous, compact, and of equal size. The Supreme Court in Wood v. Broom (1932) ruled that those provisions were no longer in force. Thus, voters complaining of the inequity of districts of grossly unequal population and of gerrymandering could find no law in effect to prevent such practices. Not until Baker v. Carr in 1962 did the Court reverse itself and rule that federal courts could review apportionment cases. In 1964, in a six-to-three decision, the Supreme Court decided the case of Wesberry v. Sanders, ruling that congressional districts must be substantially equal in population. Departing from the precedent established in Baker, and also in Reynolds v. Sims earlier in the same year, the Court did not use the Fourteenth Amendment as its justification but based its decision on the history and wording of Article I, section 2, of the Constitution. The Court stated that this language means that "as nearly as is practicable, one man's vote in a congressional election is to be worth as much as another's."

The Supreme Court has also played a key role in the apportionment of state legislatures. Until the Supreme Court ruling in Baker v. Carr, constitutional standards by which apportionment should be measured were not established. In a group of six state legislative reapportionment cases—collectively known by the name of the first case, Reynolds v. Sims (1962)—the Supreme Court made these major points: the Fourteenth Amendment's equal protection clause "requires that the seats in both houses of a bicameral state legislature must be apportioned on a population basis"; "mathematical exactness of precision" in carving out legislative districts may be impossible, but apportionments must be "based substantially on population"; "the so-called federal analogy is inapplicable as a sustaining precedent for state legislative apportionments"; and deviation from the one man, one vote rule for both houses is unconstitutional even if endorsed in a statewide initiative process or referendum because "a citizen's constitutional rights can hardly be infringed upon because a majority of the people choose to do so."

The equal population (one man, one vote) principle enunciated in Reynolds brought relief from decades of mal-apportionment. In spite of what the 1920 census revealed about urban and rural population, many state legislatures had refused to reapportion either congressional districts or state legislatures to reflect the change in population, thus allowing the rural areas to continue to hold the reins of political power. Rural areas were also legally favored in those states in which the state constitutions provided apportionment based partly or wholly on counties or towns rather than on population. The majority opinion in Reynolds did not attempt to spell out precise state constitutional tests because "what is marginally permissible in one state may be unsatisfactory in another." It endorsed a case-by-case development of standards and seemed to be requiring a good-faith effort to achieve "precise mathematical equality." Left unresolved were requirements for compactness and contiguousness of districts, and the constitutionality of multimember districts. By the early 2000s, apportionment remained a highly contentious and partisan issue, one that neither the Supreme Court nor the Congress had completely resolved.


Cain, Bruce E. The Reapportionment Puzzle. Berkeley: University of California Press, 1984.

Eagles, Charles W. Democracy Delayed: Congressional Reapportionment and Urban-Rural Conflict in the 1920s. Athens: University of Georgia Press, 1990.

Schwab, Larry M. The Impact of Congressional Reapportionment and Redistricting. Lanham, Md.: University Press of America, 1988.

Calvin B. T.Lee/a. g.

See alsoCongress, United States ; Connecticut Compromise ; Preferential Voting ; Primary, White ; Suffrage: Exclusion from the Suffrage .

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The term apportionment refers to the decennial process that divides membership in the U.S. House of Representatives among the fifty states according to the size of the states populations. After apportionment, state governments initiate redistricting, the highly contentious process of revising the intrastate boundaries of the House districts. Article I, Section 2 of the U.S. Constitution mandates that apportionment take place every ten years, and Congress is given the responsibility of managing the procedure. Two amendments to the Constitution influence apportionment: Amendment 14, Section 2 repealed the original provision that considered nonfree persons (slaves) as three-fifths of a person for counting purposes, and Amendment 16 released the federal government from the original bind of having to use a states population as a basis for determining tax levies.

The Constitution entitles each state to have at least one representative in the House, with the respective numbers of each of the states forming the basis for the further distribution of seats. Congress has the power to define the precise manner of dividing up House seats, and this process has been a continuous source of controversy. In issuing his first presidential veto, George Washington rejected a formula designed by New Yorks Alexander Hamilton for allocating seats after the 1790 census (Prewitt 2000, p. 2). More recently, a 1998 U.S. General Accounting Office paper noted that after the number of available House seats was fixed at 435 in 1911, a gain of representation for any one state came only with a loss of representation for another state (p. 10). Orville J. Sweeting notes that the cap was instituted because the House threatened to become so large, if size continued to follow population growth, that it could not properly transact its business (1956, p. 440).

Southern and rural members of Congress were so fearful of the consequences of losing their seats due to the urban and northward shift of the population that they prevented the constitutional mandate of apportionment from taking place during the 1920s. Although apportionment has occurred in every decade since the 1930 census, the political battles associated with the process have not subsided. As currently written, Title 2 of the U.S. Code requires the use of the method of equal proportions to determine the allotment of seats among the states, as described in an online document produced by the Census Bureau. This method has been in place since the apportionment associated with the 1940 census, and it was upheld as constitutional by the Supreme Court in 1992 in the case of United States Department of Commerce v. Montana.

In the prelude to the 2000 census, there was a strong debate over whether statistical sampling to adjust for census undercounting could be used in the apportionment process. In 1999, the Supreme Courts five-to-four ruling in Department of Commerce v. United States House of Representatives affirmed that Section 195 of Title 13 of the U.S. Code prohibits the use of statistical sampling, but the Court explicitly declined to rule on the constitutionality of using sampling should this section of the code be repealed.

SEE ALSO Census; Congress, U.S.; Gerrymandering


Prewitt, Kenneth. 2000. The US Decennial Census: Political Questions, Scientific Answers. Population and Development Review 26 (1): 116.

Rush, Mark E., and Richard Lee Engstrom. 2001. Fair and Effective Representation?: Debating Electoral Reform and Minority Rights. Lanham, MD: Rowman and Littlefield.

Sweeting, Orville J. 1956. John Q. Tilson and the Reapportionment Act of 1929. Western Political Quarterly 9 (2): 434453.

U.S. Census Bureau. 2001. Computing Apportionment Homepage.

U.S. General Accounting Office. 1998. Decennial Census: Overview of Historical Census Issues. Washington, DC: U.S. Government Printing Office.

Thomas J. Scotto

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"Apportionment." International Encyclopedia of the Social Sciences. . 23 Apr. 2017 <>.

"Apportionment." International Encyclopedia of the Social Sciences. . (April 23, 2017).

"Apportionment." International Encyclopedia of the Social Sciences. . Retrieved April 23, 2017 from