The most widely accepted rule for redistricting is that districts should be relatively equal in population. This is because representation by population is a central tenet of democracy, and, in countries that employ single-member districts, this rule translates into the principle of equal populations across districts. Equally populous districts are necessary if voters are to have an equally weighted voice in the election of representatives. If, for example, a representative is elected from a district that has twice as many voters as another district, voters in the larger district will have half as much influence as voters in the smaller district.
The degree to which countries require population “equality” and the population figure (for example, total population, citizen population, registered voters) that is used to determine equality differs across countries. Approximately half of the countries that delimit districts use “total population” as the population base for determining equality across electoral districts. Another third of the countries employ registered voters as the population base. Several European countries use citizen population as the relevant base for determining population equality. Lesotho uses the voting age population as the base; Belarus uses the number of voters in the previous election.
The degree to which countries demand population equality also varies. Many countries have no established tolerance limit regarding the extent to which constituencies are permitted to deviate from the population quota. Among those that have established limits there is a range from “virtually no deviation allowed” (the United States) to as high as a 30 percent tolerance limit (Singapore).
Deviations from Population Quotas
Minimal
The United States is unique in its adherence to the doctrine of equal population. No other country requires deviations as minimal as the “one person, one vote” standard that has been imposed by U.S. courts since the early 1960s. In the 1983 court case Karcher v. Daggett, the U.S. Supreme Court held that there is no point at which population deviations in a congressional redistricting plan can be considered inconsequential: “there are no de minimus variations which could practically be avoided but which nonetheless meet the standard of Article I, Section 2 [of the U.S. Constitution] without justification.” The Court went on to reject a New Jersey congressional redistricting plan that had a total population deviation of only .7 percent. Following this decision, most states interpreted Karcher as requiring the adoption of congressional redistricting plans with exact mathematical population equality or, at minimum, with the lowest possible population deviation. Although the courts later upheld the legality of some redistricting plans that had less than the absolute de minimus population variation possible, none of the plans upheld contained total deviations of even one percent.
Medium
Macedonia, with a Regional List PR electoral system and six electoral districts, comes closest to this strict standard, with allowable deviations of no more than plus or minus three percent from the population quota. New Zealand, Albania, and Yemen allow deviations of up to five percent from the population quota. Australia, Belarus, Italy, and the Ukraine specify 10 percent as the maximum allowable deviation.
The population requirement in Australia, however, is actually more complicated than a 10 percent tolerance limit: Australian election law also requires that electoral districts deviate by no more than 3.5 percent, three years and six months after the expected completion of the redistribution. This criterion was devised to produce equality of population halfway through the seven-year Australian districting cycle and to avoid wide discrepancies at the end of the delimitation cycle. To meet this requirement, the Australian delimitation commission (referred to as the Redistribution Commission) must use population projections as well as current population data.
Australia's close attention to population equality is relatively recent. Thirty years ago, the practice of heavy rural loading--creating rural districts that were much smaller in population than urban districts--was quite common. (For more information on Australian redistricting practices, see the case study on Australia, Federal Redistribution in Australia.)
Large
Armenia, Germany, and the Czech Republic allow population deviations of no more than 15 percent. (In Germany, proposed electoral districts cannot deviate by more than 15 percent, and districts that deviate by more than 25 percent must be redrawn.) Zimbabwe and Papua New Guinea have set the maximum allowable deviation at 20 percent.
In Canada, the independent commissions charged with creating federal electoral districts are allowed to deviate by up to 25 percent from the provincial quotas. But since 1986, commissions have been permitted to exceed the 25 percent limit under "extraordinary circumstances." This provision was used to create five of the 295 seats in the Canadian House of Commons in 1987, two of 301 seats in 1996 and two of 308 seats in 2003. In 2003, one Ontario district was 43.7 percent below the provincial average and one Newfoundland district was created with a population 61.9 percent below the provincial average (For more information on Canadian redistribution, see the case study on Canada, Representation in the Canadian Parliament.)
The United Kingdom allows even larger deviations in district populations. The original standard was set at 25 percent in 1944. But the standard was repealed only two years later. The current rule however requires that constituencies be "within plus or minus five percent of the United Kingdom quota", but this rule must be balanced against other factors such as local boundaries and special geographical considerations. Allowances for natural communities prompted English boundary commissioners in 1983 to leave the Isle of Wight with 95,000 electors as a single constituency, while respect for local London boundaries left suburban Surbiton with only 48,000 electors. The last redistribution saw the Isle of Wight apportioned an additional district, the two districts having 56,000 and 55,000 electors respectively. Likewise, recognising the difficulties of island travel, the commissioners in Scotland granted the Western Isles (2011 population 22,000) and Orkney and Shetland (2011 population 34,000) their own representatives.
Conclusion
The degree to which a country adheres to strict equality of population is related to the significance attached to individual political equality. The United States is strongly committed to individual rights, so perhaps it is not surprising that it developed the strictest population deviation standards of any country using single-member districts. Other countries, while recognising the importance of population equality, have chosen to balance this factor against other redistricting criteria perceived as equally valid. In the United Kingdom, respect for local administrative boundaries is given precedence over exact equality of number. In many African countries, the need to keep individual tribes intact in a single electoral district may take precedence over population equality. Each country must determine how much variation from the ideal of exact population equality will be tolerated to accommodate other redistricting goals.
