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.