Tasks Involved in Drawing Electoral District Boundaries

The process of drawing electoral district boundaries is time consuming and labour-intensive. The delimitation process usually begins with an allocation of seats to sub-regions of a country, such as states or provinces. Seats are almost always allocated to regions on the basis of population. But under special provisions, certain regions may receive more or fewer seats than population alone would dictate.

Once seats have been allocated, the process of drawing district lines within a region commences. A redistricting database is created using population data and, in some countries, political data as well. Maps are collected. After all of the necessary information has been gathered and synthesised, the process of assigning geographic units to electoral districts can begin. Each geographic unit--whether it is a county, city, town or village, or some smaller geographic census unit or voting area--is assigned to a specific district. After all geographic units in the region have been assigned to one and only one electoral district, the plan is complete and ready to be evaluated.

The process for evaluating a redistricting plan depends in large part on the redistricting criteria that have been adopted. A statistical summary of population or other demographic data by district is straightforward as long as the requested data has been included in the redistricting database. The plan may require a more sophisticated or subjective assessment, as well, depending on the criteria adopted. For instance, are communities of interest intact? Do minority voters have an opportunity to elect candidates of their choice?

Computers can be used to make the drawing of district boundaries more accurate and efficient. Consultants can be brought in to assist in any aspect of the redistricting process. A decision on whether computers or consultants should be employed depends on the need for them and what they will cost.

This section discusses the information needed to conduct redistricting: population data, maps and political data (see Information Required to Draw Electoral Districts). It outlines steps in the line drawing process, including the allocation of seats, the preparation of a database, the drawing of district boundaries, and the summary description of the plan for evaluation (see Steps in the Electoral District Delimitation Process). And it considers the possible use of computer technology and/or consultants (see Computer-Assisted Delimitation and Use of Consultants).

Information Required to Draw Electoral Districts

Delimitation, or redistricting, requires the collection of several different types of information. The two essential pieces of information are population data and maps. The population data, which may be in the form of census enumeration data or voter registration data, provide the only means of creating districts that are relatively equal in population. The population data must be associated with a specific geographic area and must be as accurate and up-to-date as possible. Maps are needed to ensure that only contiguous geographic population units are assigned to districts.

A third piece of information that may or may not be utilised for redistricting is political data. Political data usually refers to election results --tabulations of votes for candidates and ballot measures from previous elections by voting area. Including political data in the redistricting database allows line drawers to produce a political profile of proposed districts and to predict, to some degree, the partisan implications of a redistricting plan.

Election results can easily be entered into the redistricting database if they are reported for the same geographic unit as the population data. This will likely be the case when the population units for redistricting are based on voter registration data. If, however, the population units are based on a census enumeration, the geographic units for population and political data may not be the same. In that case, census geography and election geography may have to be matched in some manner to create geographic units that can be associated with both population and political data.

In the United States, for example, electoral districts are usually created using census geography (census blocks or tracts), but election results are reported at the voting area (election precinct) level. These two units of geography--census blocks and election precincts--are not equivalent. States that wish to use political data in conjunction with population data must develop some method of matching political data with the corresponding units of census geography.

Use of Population Data in the Delimitation Process

Population data is essential to the redistricting process. Redistricting operates by combining discrete geographically-based units of population in a series of assignments designed to produce districts of relatively equal population. The population data can be either total population counts based on a census enumeration or voter registration data; the geographic population units will therefore reflect either census geography or election geography (these units of geography are often, in fact, the same).

The Use of Census Enumeration Data

In the United States, the reapportionment of the House of Representatives of the Congress and the redrawing of congressional districts have always been based on a census count of the total population. The number of seats to which each state is entitled in the U.S. Congress is dependent on the relative size of the state's population according to the census enumeration. The U.S. Constitution requires the Census Bureau to conduct an enumeration of the entire population every ten years.

Therefore, a national census is conducted as of April 1 in the first year of each decade (for example, 1980, 1990, and 2000). The Bureau must report the results of the census to the president by December 31 of the census year. Since 1975, the Census Bureau has also been required to send population data specifically for redistricting purposes to each state governor within a year of conducting the census.

The redistricting data produced by the Census Bureau is referred to as PL 94-171 data (for Public Law 94-171). It includes population counts for several different levels of census geography, i.e., units as large as whole counties and units as small as census blocks (usually the equivalent of one city block) are reported in PL 94-171.

Although the Census Bureau collects data on a large number of population characteristics, only a few items are included in the data files sent to the states for redistricting. These items are total population, voting age population, and subtotals of the population for persons of Hispanic origin and for five major racial groups--white; black; Asian and Pacific Islander; American Indian, Eskimo, and Aleut; and "other" races. Population data by race and Hispanic ethnicity are needed to ensure that communities in which these minority groups predominate are not divided by electoral district boundaries. (An example of PL94-171 population data reported at the city level can be found in U.S. census population data for redistricting.)

Because children and non-citizens are counted in the U.S. census, the population base for redistricting in the United States includes many persons not eligible to vote. In the United Kingdom and many other countries, especially those with compulsory voter registration, the redistricting base is the number of qualified voters rather than the total population. The use of qualified voters as the redistricting base automatically eliminates children and non-citizens from the calculation. Whether this practice makes sense from the perspective of democratic representative theory is arguable.

The use of census population data as the redistricting base presents some problems, such as:

• census data may be inaccurate;
• census data can become obsolete;
• population equality does not necessarily produce an equal electorate.

 

 

Inaccurate Census Data

The U.S. Census Bureau estimates that in 1990 it undercounted the population by 1.6 percent. If certain racial or ethnic groups are undercounted at a higher rate than others groups, both the allocation of seats in a legislative body and the redrawing of legislative districts can be affected. Blacks in the United States, for example, were undercounted in 1990 at a much higher rate (approximately 5 percent) than the population in general. If a state is disproportionately undercounted because it has a large black minority population, the state could conceivably lose a congressional seat when the Congress is reapportioned.

Obsolete Census Data

Even if it is accurate at the time of enumeration, census data can rapidly become obsolete because of growth rates. The use of census data for redistricting may discriminate against localities experiencing high population growth, such as, for example, suburban areas in the United States. Over time, people in these suburban districts will become underrepresented compared to those in rural or urban districts.

Census Data May Produce Unequal Electorates

Even if all districts are drawn such that they have the exact same population, the number of electors per district would not necessarily be equal because the proportion of nonvoters—that is, noncitizens, those too young to vote, and even registered voters who choose not to cast a ballot – is not uniform across the population. In the United States, for example, a congressional district with a large Hispanic population is likely to have more children and more non-citizens than a district with few Hispanics. For this reason, the number of voters on Election Day is likely to be lower in the heavily Hispanic district than in other districts.

The Use of Voter Registration Data

These same problems affect the use of voter registration data as the redistricting base, although not to the same degree. Unless the registration system is very accurate, the registration count could be incorrect. For example, the registration rolls could be inflated due to failure to remove from the list deceased persons or persons who had moved from the district; alternatively, the rolls could be missing some potential voters if the lists are not updated often enough. And unless voting is compulsory, some registered voters may neglect to cast ballots on Election Day, making the number of voters unequal across districts. After some period of time, population shifts will render districts of unequal size, regardless of whether population or registration counts are used.

Australia has adopted a unique solution to the problem of population shifts over time. Federal electoral districts are redrawn in Australia using registration, or enrolment, figures--but not current enrolment figures. Instead, districts are redrawn based on projections of what the enrolment of each locality is likely to be in three and a half years, the midpoint of the redistribution period. (See the case study, "Federal Redistribution in Australia"en.bdy_au, for more information on the use of population projections.)

Conclusion

The choice of whether to use census data or voter registration data may be guided by either practical or theoretical concerns. For instance, reliable registration data may simply not be available or may not be adequate for redistricting purposes. In the United States, for example, racial data is needed to ensure that minority communities are not divided between districts, and racial data are usually not available from the registration rolls. On the other hand, registration rolls may provide the better measure of the current population when a general enumeration of the population is unavailable, outdated, or inaccurate.

Redistricting based on registration data is likely to produce districts that are more equal with regard to the number of voters contained in them. But are voters the only persons deserving of representation? From the point of view of democratic theory, an argument could be made that all persons, and not simply voters, should be represented. If a broader definition of "representation" is adopted--one that views representatives as acting on behalf of all his or her constituents, non-voters as well as voters--then the justification for the use of total population is that it produces equal constituent representation in a more expansive sense[1].

Notes:

[1] This discussion draws heavily from an article written by Carlton Henry entitled "The Impact of New Technology and New Census Data on Redistricting in the 1990s," in Redistricting in the 1990s: A Guide for Minority Groups, ed. William O'Hare (Population Reference Bureau, Inc., 1989)

Use of Political Data in the Delimitation Process

Because population data does not provide information about the political composition of a proposed district, political data is sometimes added to a redistricting database. Political data may include statistics on the partisan affiliation of electors (if available) and tabulations of votes for candidates and ballot measures in prior elections. When political information is included in a redistricting database, it may be possible to predict how support for a particular candidate or political party might be affected by a change in the geographic composition of a district.

The major consumers of political information in the redistricting process are political parties and incumbent legislators. Political parties are interested in determining how changes in district boundaries are likely to affect the election of their candidates and, ultimately, the partisan composition of the legislature. Incumbent legislators, of course, are interested in ensuring that they will continue to be re-elected by the voters in their new districts.

In the United States, the courts are also interested in political information, but usually for very different reasons. Under the Voting Rights Act of 1965, certain minority groups are protected from redistricting plans that might dilute the effect of their vote. The courts use election results from prior contests in minority vote dilution claims to determine if there is (1) minority group cohesion in support of certain candidates and (2) bloc voting on the part of white voters against the minority group's preferred candidates. If these two conditions are met, and if the minority group is sufficiently large and geographically compact, then boundaries must be redrawn to create a district in which the minority community has the opportunity to elect a representative of its choice. (For more information on minority vote dilution cases in the United States, see Role of the Courts in Electoral District Delimitation.)

Problems with Using Political Data for Redistricting

Adding political data to a redistricting database may be problematic since election geography may not correspond with census geography. In the United States, for example, where census geography is usually used to redraw districts, the Census Bureau requires that census geographic units--census blocks and tracts--follow easily recognised features, such as roads and rivers. The boundaries of election precincts, however, have historically been based on property lines and therefore do not necessarily coincide with the boundaries of census geographic units.

If political data is added to a redistricting database in the United States, the data must somehow be matched to its corresponding census geography. This process can be difficult and time-consuming, as well as fraught with inaccuracies. Countries that redistrict on the basis of voter registration figures do not face this problem since registration figures and political data are usually reported at the same geographic level.

Advantages and Disadvantages of Political Data

The primary disadvantage associated with the use of political data is that it enables redistricters to create a districting plan that may favour one political party at the expense of others. In countries that have neutral boundary commissions, political information is often purposely excluded from redistricting databases to prevent political gerrymandering. Of course, political parties with sufficient resources may collect their own political data to learn in advance about the potential partisan implications of a redistricting plan.

The advantage of including political information in a redistricting database is that the partisan implications of a new redistricting plan may be determined prior to its implementation. And the ability to make such a determination is not limited solely to political parties or special interest groups with sufficient funds to carry out the necessary analysis. Since any changes in boundary lines are likely to have partisan consequences, whether intentional or not, it may be better to know in advance what these effects will be.

Of course, the partisan impact of a redistricting plan is not necessarily predictable, especially if voters are not strongly partisan. It is an inexact science in any case, and some rather infamous gerrymandering has backfired on their creators.

Use of Maps in the Delimitation Process

Maps are essential in the redistricting process, but obtaining adequate maps can be one of the most challenging obstacles facing redistricters. While standard maps, such as road maps, identify geographic features and the boundaries of administrative areas such as counties, cities and towns, they may not necessarily provide sufficient detail for drawing electoral districts.

If redistricting is based on a census count of the population, then the maps must show the boundaries of the census geographic units for which population statistics are available. If redistricting is based on the number of registered voters, then the maps must show the boundaries of the voting areas for which voter registration statistics are available. The boundaries of the existing electoral districts are usually needed as well.

Considerable time and effort may be needed to assemble the necessary maps and to determine the precise boundaries of the new district lines on these maps. Sufficient detail is needed to enable election administrators to assign each and every voter to an electoral district. This can be a very difficult and time-consuming process, even for jurisdictions with technologically sophisticated computer mapping systems.

In the United States, maps provided by the Census Bureau were once drawn by hand and, as a result, were often difficult to read and frequently filled with errors. In preparation for the 1990 census, however, the Census Bureau created a computerised database of the entire country called TIGER (Topographically Integrated Geographic Encoding and Referencing). The TIGER database depicts:

• visible geographic features such as roads, rivers, and railroads;
• a whole hierarchy of census geographic units (for example, census blocks, block groups, and census tracts) for the collection and reporting of population data;
• the boundaries of administrative subdivisions such as counties, cities and towns; and
• political geography such as congressional districts and, in some cases, voting areas, referred to as election precincts in the United States

Maps produced from the TIGER database for use with GIS (geographic information systems) software provide redistricters in the United States with uniform, digitised maps on a county-by-county basis for the entire country. The availability of these maps has made the process of district building in the United States more accurate and less time consuming.

Very few countries, however, have computerised maps available for redistricting purposes – most redistricters have access only to paper maps. Depending on the country, there can be serious problems with accuracy, legibility and differing scales with these paper maps. Digitised computer maps of the country can be created, but only at an enormous cost. Of course, these detailed computer maps can be used for many purposes other than redistricting and, therefore, may be worth the time, effort and expense.

Steps in the Electoral District Delimitation Process

There are usually two phases in the electoral district delimitation process. The first phase is the allocation, or apportionment, of seats in the legislature to regional entities such as states or provinces. This is usually a very mechanical process, with the number of seats assigned to each state or province usually dependent on the relative population of that state or province. In countries that do not delimit single-member districts, the reallocation of seats, or reapportionment, is the only step taken to equalize population across electoral districts.

In countries that do redistrict, the second phase of the process is usually the adjustment of the boundaries of current districts and/or the creation of new districts within the states or provinces themselves. In countries that do not allocate seats regionally, this is the only phase in the process.

Drawing electoral district boundaries is much less mechanical and much more time consuming than allocating seats. It proceeds in three stages:

• preparation of a redistricting database
• assignment of geographical units to districts until all units have been assigned and the boundaries of all districts established
• production of a summary description and maps for evaluating and implementing the redistricting plan

Allocating Seats

Many countries, especially those very large in size and/or having a federal system rather than a unitary system, delegate the responsibility for drawing national legislative districts to regional entities such as states or provinces. For example, in the United States, seats in Congress are allocated to the states on the basis of each state's relative population. Each state is then responsible for drawing the prescribed number of congressional districts within its borders. Australia and Canada use a similar system of allocating seats in the national parliament to the states or provinces and then having independent electoral commissions in each state or province draw district boundaries.

In the United States, the decennial process of allocating congressional seats among the states is called "reapportionment." In Canada, the decennial reallocation of Parliamentary seats among the provinces is known as "redistribution." But in many countries, no special terminology is applied to this allocation process. This is especially true of countries that do not have federal systems or countries where regional entities have little power over redistricting decisions. Population (either census enumeration data or voter registration figures) is almost always used as the basis for apportioning seats to national legislatures. In fact, the stated purpose of decennial census in the United States is to determine the proper allocation of congressional seats among the states. The U.S. Constitution, in Article I, Section 2, provides that:

“Representatives shall be apportioned among the several states...according to their numbers....The actual Enumeration shall be made within three years after the first meeting of the Congress and within every subsequent term of ten years in such manner as they shall by law direct.”

Before seats are allocated, however, the total number of seats in the legislative body is often determined. But this is not always the approach adopted. In its first 120 years, for example, the U.S. House of Representatives simply grew in size to accommodate new states and a rapidly growing population. From 1790 to 1900, seats were allocated to states on the basis of a population quota which, despite its gradual increase over time, resulted in the House of Representatives expanding in size from 106 to 391 during this time period. Since 1910, however, a permanent ceiling on membership in the House of Representatives has been set at 435 legislators. Seats were allocated by first giving each state one seat and then awarding the remaining seats in succession to the states with the largest remaining quota. In 1950, the statute defining the formula was modified slightly. Each state was given one seat, and the remaining 385 seats were allocated in succession under a priority numbers formula. This formula is referred to as the "method of equal proportions.”

Although the process is a mechanical one, the formula for the allocation of seats has not escaped controversy. Since 1790 states in the United States have argued over how congressional seats are apportioned, and states that have lost representation have been especially sensitive about the process.

Some countries have adopted solutions designed to alleviate this problem. Canada, for example, has solved this problem by never allowing the number of seats allocated to a province in the House of Commons to decrease. Canada, like the United States, requires that the distribution of seats in the House of Commons be governed by the "proportionate Representation of the Provinces," based on a decennial census. However, a "grandfather clause" was adopted to protect provinces with declining populations relative to the other provinces. This clause, first enacted in 1976 and then re-enacted in different legislative form nine years later, ensures that no province can ever have fewer electoral districts than it had in 1976. The size of the House of Commons has gradually increased as a result. (For more information on the redistribution process in Canada, see the case study Representation in the Canadian Parliament.)

There are two problems with allowing states or provinces to retain more seats than population alone would dictate:

• the size of the legislature could become unwieldy;
• the population or electoral quota (the population of the state divided by the number of seats allocated to the state) can vary considerably across states or provinces.

The latter occurs when a state or province is awarded a greater number of seats than it would normally be entitled, based on its relative proportion of the population. In Canada, these are referred to as "add-on" seats.

But a broad range in population quotas is possible even without add-on seats. In the most recent round of congressional redistricting in the United States in 1991, the population quota for congressional districts ranged from 455,975 in Wyoming to 803,655 in Montana. This broad range occurred because each state is awarded at least one seat, even if its population is below the "national quota" for a seat. No national electoral quota is actually applied in the United States; quotas are calculated only on a state by state basis. The population of the state of Wyoming was below the "national quota" for a congressional district, but was awarded a seat; whereas the population of Montana, more than ample for one congressional seat, was not quite large enough to be allocated two seats.

Drawing District Boundaries

Drawing electoral district boundaries is the second phase of the redistricting process. The drawing of federal electoral districts can either be done at the federal level or at the state or provincial level, once a specified number of districts have been assigned to the state or province. Drawing district lines proceeds in three stages:

• preparation of a redistricting database
• assignment of geographic units to districts, forming district boundaries
• production of a summary description and maps of the redistricting plan

Preparation of a Database

Before line drawing can commence, a redistricting database must be created. The database is composed of all of the geographic units that are to be used as the building blocks, and any population data, as well as any additional demographic and political data associated with these geographic units and deemed useful for redistricting. The geographic units may be as large as counties, cities or towns, or as small as voting areas or city blocks.

Formation of District Boundaries

After the database has been created, district boundaries can be formed. This involves adjusting the boundaries of existing districts and/or creating new districts. The process entails assigning, or reassigning, geographic units to districts until all units have been assigned to the requisite number of districts.

Production of a Summary Description and Maps

After the districts have been formed, a summary description of the redistricting plan must be produced. This description usually consists of a list of the geographic components of each district, a map of the district plan, and a statistical summary of the districts using selected population and possibly political data. This information may be used to evaluate the redistricting plan on a variety of levels, such as equal population, and is needed to implement the plan for election purposes.

Preparing a Districting Database

The first step in the line drawing process is preparing a database. In a redistricting database, each data item reflects a single geographic unit. The geographic units, to be used as the basic building blocks for creating the districts, can reflect administrative areas such as counties or cities and towns, census geography such as census blocks, or election geography such as voting areas. The database should include as much of the following information as possible for each geographic unit:

• a unique name or identification number for each unit
• additional identifiers, such as town or city, county, and state or province for each unit
• the total population or the number of registered voters for each unit

Additional demographic data, such as total population and voting age population counts by race or ethnicity for each unit, may also be included if useful for redistricting.

The Use of Digitised Geographic Data

If geographic information systems (GIS) software is to be used to develop district plans, the redistricting database must also include information related to the location of the geographic unit (spatial co-ordinates). This information allows the computer to automatically generate computer screen maps that reflect each new assignment of a geographic unit to a district.

The Use of Political Data

If the redistricting database is to include political information, then voter registration counts by political party, if available, and votes for candidates from previous elections should be entered for each geographic unit. The number of previous elections to be included in the database depends on the availability of previous election results, the amount of time required to enter the results into the database, and the financial resources available for creating the database.

If a redistricting database is to include both political and census demographic data, the election geography and the population geography must correspond with one another. If they do not, they will have to be matched.

Matching Census and Election Geography

Matching census geography and election geography can be quite challenging. The easiest method for matching these units is to merge the smaller geographic units until they approximate the boundaries of the larger unit. If, for example, census data is available for units as small as city blocks, then these blocks can simply be aggregated together until they match an election precinct (voting area). On the other hand, if the units of election geography are smaller, then they can be merged to produce political data for the larger pieces of census geography (e.g., villages and towns). It is always easier to aggregate data up to the higher level than it is to try and break it down to smaller levels of geography.

In the United States, however, the courts often require states to draw districts with census geography rather than election precincts (voting areas). This requirement can be handled in one of two ways:

• election precincts and their corresponding political data can be merged until they approximate census tracts;
• alternatively, precinct level election results can be disaggregated down to the census block level.

If redistricters want the flexibility of being able to draw at the smaller census block level (and many states do, in fact, prefer this approach), then political data reported at the precinct level have to be disaggregated and distributed among the census blocks that fall within that election precinct. This process is difficult, involves a great deal of estimating, and is subject to a great deal of error. Because it is a very tedious and labour intensive task, it will absorb a substantial amount of the database construction time.

Drawing Electoral District Boundaries

Once a database has been prepared, the next step in the redistricting process is the formation of districts. This is the step in which the line drawers create a redistricting plan either by assigning geographic units to districts for the first time or by moving geographic units in an existing plan from one district to another. A redistricting plan is complete when all geographic units in a given territory are assigned to a district and all districts in the plan meet the predetermined redistricting criteria. The geographic units to be assigned may be as large as counties or cities and towns, or they may be smaller units of geography such as census blocks or voting areas.

If the line drawers are to create a new redistricting plan by modifying districts in an already existing plan, their tasks may be relatively straightforward. This is especially true if a decision has been made that districts should be modified only as much as necessary to meet equal population standards. Many countries, for instance, list consideration of existing district boundaries as a redistricting criterion. If there is no existing redistricting plan to modify or if the number of districts in an existing plan is to change substantially, the line drawers' tasks become more challenging.

Modifying Districts in an Existing Plan

One strategy that could be adopted if districts already exist and simply need to be modified is to (1) determine the current population of each of the existing districts, (2) calculate the minimum amount of change required to meet equal population standards, and (3) focus only on the districts that need to add or subtract population. Of course, it is never as simple as adding or subtracting population only from the malapportioned districts. Since the process also affects adjoining districts, a ripple effect usually occurs across the districts, necessitating at least some changes to other districts. But an effort could be made to minimise these changes.

This incremental approach to redistricting is often adopted by line drawers who are required to consider existing district boundaries when redistricting. It may also be a good strategy if the legislative body for which new districts are being drawn must approve the redistricting plan before it can be implemented. The chances of obtaining legislative approval for a redistricting plan are obviously affected by the extent to which existing districts are disrupted. In the United States, for example, the wisest strategy is often to move only the minimum amount of geography necessary to achieve population equality – this ensures bipartisan legislative support for the redistricting plan.

Creating a New Plan or Substantially Modifying a Plan

Drawing districts where districts have not previously existed or where district boundaries must be changed substantially is a more complex process. The task of drawing districts for the first time can be simplified by dividing a large territory into manageable sub-regions and drawing districts in two or three stages. If a country is divided into states or provinces, for example, allocating districts first to the states or provinces and then drawing districts within these states or provinces will make the process more manageable. A second level of district allocation may also be desirable if the states or provinces are large. If further allocations are made, however, the subdivisions should possess some sense of geographic unity.

Choosing the Basic "Building Block"

One of the first decisions to make in creating districts is what unit of geography and, possibly, what level of geography to use as the basic building block. This decision is required whether the line drawers are to modify an existing districting plan or create an entirely new plan. Whether composed of census or election geography, the redistricting database has, presumably, been built upon a unit of geography small enough to give the line drawers some flexibility in creating districts.

The line drawers, however, need not use the smallest unit of geography available in the redistricting database as the only building block when creating or modifying a plan. For example, redistricters may be able to assign whole counties or cities in many areas and resort only to individual census blocks or voting areas in certain, usually urban, areas. And, in fact, it is easier and faster to create the broad outlines of districts with large geographic units and then use the smaller units to make the refinements necessary to comply with equal population standards or other redistricting criteria.

Choosing Where to Begin Drawing Districts

Another decision that should be made early in the process of creating districts is where to begin drawing district lines. Redistricters often begin at the corners of a territory and work towards the centre. This is done to avoid any distortion which may result at a corner or edge if the process starts at one side of the territory and moves to a final corner or edge.

There may be reasons to begin the line drawing elsewhere. If, for example, the redistricters wish to create a district for a geographically concentrated minority community or some other community of interest, they may begin by drawing the boundaries of that particular district and then move the line drawing process outward from that district.

Drawing District Boundaries Interactively

Once decisions have been made about what units of geography to use as building blocks and where to begin the line drawing process, the actual line drawing can commence. The line drawing process is an interactive one. The redistricters assign a piece of geography and then determine how the inclusion of that particular geographic unit affects the size and composition of the district.

Although aggregating the population totals for the districts after each new assignment is a straightforward process, it can be a tedious one as well. And as geographic units continue to be shifted, this process is repeated over and over again. A computer can automate this process, but it can also be done manually with a hand-held calculator, if necessary.

Describing and Evaluating an Electoral District Plan

Once the boundary authority has successfully completed a redistricting plan by assigning all geographic units in the territory to a district, summary information for the plan should be produced. This information may be used to evaluate the plan. Also, it is often needed to prepare legislation in order to enact a plan. Certainly, it will be needed to implement a plan once the final plan has been approved. A summary description of a redistricting plan should include:

• a description of the plan listing the geographic components of each district
• map(s) of the plan showing the district boundaries
• a report summarising the most relevant statistical information for each district in the plan

Description of the Plan

A description of the redistricting plan should include a detailed list of all of the geographic units contained in each district. A narrative description of the plan could also be created. In the United States, for example, a detailed street-by-street description of district boundaries, called "metes and bounds," is often required, especially in urban areas.

Examples of descriptions of redistricting plans enacted by various states in the United States--listed by census units, election precincts and metes and bounds--can be found in United States: Election Laws from varoius states (1996)

Maps of the Plan

Maps of the redistricting plan may need to be created at different scales. A large-scale map will be needed to show the entire redistricting plan while a series of smaller-scale maps may be needed to show district boundaries in more detail in areas with higher population densities. These maps may be used to inform legislators and voters of the new district boundaries. In addition, these maps will be needed by election administrators to implement the new plan.

Summary Report of the Plan

Summary reports of the redistricting plan can be produced displaying district population totals and any other statistics for data items that have been included in the redistricting database. These reports may include detailed demographic data as well as political data, if desired. The design of the report should reflect its intended purpose. Of course, more than one report can be compiled for each plan. The only constraint on reporting capabilities is that the information must have been included in the database. For this reason, it is important to construct a database that includes as much of the necessary information as possible.

Summary reports allow redistricters to evaluate a redistricting plan according to established criteria. For example, the redistricting criteria may specify that districts be as equal in population as possible, and that some districts afford minority voters the opportunity to elect candidates of choice. In this instance, the summary report of the redistricting plan should list the total population, the population deviation from the electoral quota, and the racial and ethnic composition of each district.

Other interested groups may request summary reports for different sets of data items. Political parties and legislators, for example, may be interested in a detailed political profile of the proposed districts. A political report could include such information as the electoral history of the district. This can be calculated by summing all the previous election results for each of the geographic units included in the new district.

It is a relatively straightforward procedure to construct reports that calculate summary statistics for data items such as total population, population by race, and votes for candidates in previous political contests, provided that this information has been included in the redistricting database. But there may, or may not, be constitutional, legal, or court-specified standards that specify, for example, what constitutes an acceptable level of population deviation. If no set standards exist, then it is still a matter of discretion as to what the summary statistics tell us.

Delimitation Technology

Delimitation, or redistricting, can be accomplished using manual techniques such as colour markers, road maps, and calculators, or by using sophisticated computers and geographic information systems (GIS) software. The technology employed may change how the redistricting process is conducted, but it does not change the task of the redistricters in drawing district boundaries. Computers and computer software can, however, add a great deal of speed, accuracy and efficiency to the redistricting process.

Computers can reduce the time it takes to draw a redistricting plan, provide accurate statistical reports to help evaluate a redistricting plan, and produce detailed colour maps of the new boundaries. With computers, report and map production can be as simple as issuing a single computer command. This increase in speed, efficiency, and accuracy has changed the redistricting process to the extent that it allows line drawers to consider a wider range of district plan options. It also permits interested parties, both inside and outside of the process, to evaluate the redistricting plans more easily and more thoroughly.

Computers and computer software can be very expensive, however, and it may not be worth the investment. This is particularly true in countries with small populations and/or few districts to draw. Computer-assisted redistricting also may not be worth the investment in countries where maps have not and cannot be digitised.

In most situations, inexpensive personal computers and simple computer programs, or even adding machines or hand-held calculators, can be used with paper maps to assign geographic units to districts and to keep track of demographic and political data for the new districts. Until very recently, this was the method employed by all line drawers and is still the method used by the vast majority of redistricters outside of the United States.

Use of Computers and Software for Delimitation

Computers can be extremely useful in the delimitation process[1]. They can reduce the time required to draw redistricting plans and also aid in the evaluation of plans. They can produce detailed maps and statistics based on the demographic and political information in the redistricting database. And because computers allow redistricters to create plans more quickly, they enable redistricters to generate a larger number of redistricting plan alternatives for comparison and evaluation.

In the United States, about half the states used computers when congressional districts were redrawn after the 1980 census. In most of these states, computers were used as "super calculators" to summarise demographic and political data and to produce printouts of demographic information for the proposed districts.

Two important developments in the late 1980s contributed to a far greater use of computers for redistricting in the 1990s. These were (1) the development and the extensive use of powerful, affordable desktop computers and (2) the development of geographic information systems (GIS) software. GIS software is an integrated system for displaying demographic data on a computerised map.

By 1990, every state in the United States used computers for redistricting, and almost every state used GIS software. The move towards computer-assisted redistricting was also aided by the availability of detailed demographic and geographic data in computer readable format from the U.S. Census Bureau.

Desktop Computers

Today, a desktop computer has as much, or more, computing power than many of the expensive mainframe computers used in the 1980s. And a desktop computer is affordable. In addition, there are now a variety of inexpensive devices for printing maps.

Computer Software

Redistricters have several different options from which to choose with regard to software. A simple spreadsheet or database program can calculate the statistics that are commonly used in redistricting, such as total population, racial composition or overall population deviation from the electoral quota. Several software vendors in the United States offer database or spreadsheet programs specifically adapted for redistricting. A more sophisticated and more expensive option is GIS software.

GIS Software

There are GIS software packages available that are specifically tailored for redistricting. GIS redistricting software allows redistricters to:

• draw district plans interactively by assigning geography to districts piece by piece and seeing the results displayed on the computer immediately;
• produce maps, both on the computer screen and in printed form;
• generate statistical reports for the redistricting plan and each individual district in a plan.

Redistricters using GIS software have a variety of sophisticated tools at their disposal for creating district plans. GIS software can be used to draw new districts by assigning geographic units to districts or by moving particular geographic units out of one district and into another. The effects of the reassignment on the population, or any other demographic or political characteristics of the districts, can be immediately reflected on the computer screen. Once a new plan has been created, the GIS software, with the aid of a laser printer or plotter, can produce a map of the new district plan or any individual district. GIS software essentially consolidates all redistricting operations into one efficient system.

The resources necessary to employ computer technology for redistricting include:

• a computer (desktop or mainframe)
• spreadsheet or database software, or GIS software
• population and, if desired, political data available in electronic form (if only paper copies of the information are available, the data will have to be keypunched into the computer program)
• maps (either paper maps or digitised maps if GIS software is to be used)

Notes:

[1] This discussion draws heavily from an article written by Carlton Henry entitled "The Impact of New Technology and New Census Data on Redistricting in the 1990s." This article appeared in Redistricting in the 1990s: A Guide for Minority Groups, edited by William O'Hare and published by the Population Reference Bureau, Inc. in 1989.

Low-Technology Delimitation

In large countries, delimitation, or redistricting, can be a major technical challenge. Manipulating the enormous amount of geography and population data required to create new districts is a very complex procedure. However, redistricting in countries with small populations and/or few districts presents fewer technological challenges.

Computers and computer software may not be worth the investment in these countries.

Although computers and geographic information systems (GIS) software can speed up the redistricting process and make the process more accurate and efficient, redistricting with computers can be very expensive. This is particularly true if the maps to be used for computer-assisted redistricting have not already been digitised.

Regardless of the technology to be employed, it is necessary to obtain accurate summaries of demographic data for current districts and to re-tabulate that data as geographic units are reassigned among the districts. Simple computer programs, or even adding machines or hand-held calculators, can be used to summarise demographic data at the district level after each new geographic assignment.

Maps must be utilised during the redistricting process to ensure that the geographic units being assigned to a district are contiguous with the district. If redistricting is to be done without GIS software, district boundaries must be drawn by hand on paper maps. Drawing the boundaries of proposed districts onto transparent acetate overlays will preserve the original paper map and can facilitate the process of manually reassigning population units among districts. Once a final redistricting plan has been decided on, maps of the new district boundaries must be produced by a separate process.

Recommended resources for low-technology redistricting include:

• a computer, adding machine or hand-held calculator
• census and/or political data on paper
• paper maps

Use of Consultants

Redistricting consultants offer a wide range of services to countries contemplating or undertaking the process of drawing district boundaries. They can serve in a broad range of capacities, from providing limited advice on a particular facet of redistricting to managing the entire redistricting process.

Some redistricting consultants may be of particular use in computer-assisted redistricting. They can provide custom software, for example, or advise on the selection of software. They can assist with the acquisition of hardware and in installing redistricting computer systems. And they can provide training in system operations.

Some of the more general services a redistricting consultant may provide include:

• help in designing a formal redistricting process, including suggesting electoral law relating to the delimitation process;
• help in the construction of a redistricting database;
• strategic advice on creating districts;
• help in evaluating a redistricting plan;
• litigation support in a court challenge to a redistricting plan.

Depending on what a consultant is being asked to do, the consultant should be conversant with comparative methods of redistricting and the laws that govern redistricting, including defining and measuring redistricting criteria, and with administering and managing the redistricting process. If the consultant is being asked to help with the line drawing process itself, the consultant should have experience with:

• the use of maps and population data;
• the construction of databases (including the merging of political and census data, if applicable);
• the creation of districts;
• the evaluation of redistricting plans.

If a number of broad tasks are required, a consulting firm or a group of consultants may be of greater service than an individual consultant.

Redistricting consultants are often trained as geographers or political scientists. Whatever their training, they should be knowledgeable about the election process and electoral law, geography, political methodology and statistics as well as the redistricting process in particular. Computer-assisted redistricting may require consultants with computer-programming and other technical skills.

The costs of hiring a consultant are as wide ranging as the services offered by consultants. Using a consultant in an advisory capacity is clearly much less expensive than bringing in a consultant to oversee or actually create a database or draw districts.