In most countries that delimit electoral districts, there is some mandatory interval by which redistricting must occur. Some countries, however, notably France, have no requirement. Although there is no standard time interval, the range of intervals for redistricting is not particularly broad. New Zealand redraws its electoral districts every five years; Australia, at least every seven years; and the United States and Canada, every ten years following a decennial census.
In some countries, the stipulated time interval between redistributions has changed periodically. In the United Kingdom, for example, the first House of Commons Redistribution of Seats Act in 1944 required redistribution every five to seven years. The law was changed in 1958 to require redistribution every ten to fifteen years, because members of Parliament and political parties objected to the frequent alterations in constituency boundaries. In 1992, the interval was shortened to every eight to twelve years because of the wide population disparities that had resulted from infrequent redistributions.
Of course, the establishment of a mandatory time interval does not necessarily mean that redistricting will occur. India has not delimited its constituencies since 1973, despite a legal provision requiring redistricting after every decennial census. By a political agreement, redistributions in India have been suspended until the turn of the century.
The disadvantage of infrequent redistricting is the wide discrepancies in district populations that often result over time. Districts that are drawn with very small population deviations at the beginning of a decade, for instance, may vary considerably in size by the end of the decade.
Australia has adopted a unique solution to this problem. Rather than use current enrollment figures, federal electoral districts are redrawn using projections, such that the number of electors enrolled in each district will be equal three and one-half years into the future, the midpoint of Australia's seven-year redistricting cycle. For more information about this process, see the case study on Australia, Federal Redistribution in Australia.
Conclusion
The disadvantages of frequent redistricting are the costs in money and time to undertake the process. In addition, frequent changes to district boundaries disrupt ties between representatives and their constituencies. To determine the optimal interval, countries must balance the costs of redistricting with the benefits of maintaining districts with some measure of population equality.
