How To Redistrict

Definitions: from FairVote.org

• Census Block - Smallest unit of census geography for which population data are counted and reported. Census blocks are delineated by the Census Bureau and are generally bounded by physical features such as roads, creeks, or shorelines, but also may be bounded by invisible features such as city, county, school district, or voting district boundaries.
   
• Deviation - Amount or percentage by which a district's population varies from that district's Ideal Population. The percentage is the difference between actual population and Ideal Population, divided by the Ideal Population.
   
• District - Boundaries that define the constituency of an elected official. A district can include one or more elected legislators (Councilors).
   
• Ideal Population - Number of people that should be in each of a town or city's voting districts for exactly equal representation. This number is calculated by dividing the total city or town population by the total number of legislators (City Councilors), and then summed by the number of legislators in each district. Also called Target Population.
   
• Plan - An electoral district configuration proposal.
   
• Overall Plan Deviation - The difference between the least populated district and the most populated district, divided by the Ideal Population, expressed as a percent.

Defining Equal Representation:

U.S. Supreme Court and other precedent have established that for municipal election purposes, when the actual district population (defined by the most recent Census) is within ten percent (10%) of the Ideal Population, the district provides equal representation. Deviations greater than 10% may be acceptable if needed to meet other important representational goals, but the intent is to keep the variation as close to or below 10% as possible.

In legal challenges, the courts use Overall Plan Deviation to evaluate redistricting plans, which must be 10% or less to qualify as equal representation.

Existing Ward Calculations:

The 2010 US Census found Burlington's population had grown to 42,417 people. Currently Burlington has 14 City Councilors, elected from 7 Wards with 2 Councilors each. (Ideal Population numbers are rounded.)

• Ideal Population = 42,417 divided by 14 Councilors = 3030 People per Councilor
• Ideal Ward Population = 3030 times 2 Councilors each = 6060 People per Ward

Table 1: Existing Ward Population Deviation | PDF version |

Table 1shows that Ward 1 has too many people - its Ward Deviation of 25.3% is above the 10% legal maximum limit. Wards 4 and 7 have too few people - Ward Deviations are -16.1% and -10.9% respectively. Further, the resulting Overall Plan Deviation is 41.5%. The maximum Overall Deviation allowed by the courts is 10%, unless there are circumstances that justify higher deviations. Burlington's existing Ward Plan has become outside the legal definition of equal representation, and must be redefined.

How Redistricting Plans are Developed:

US Census population data serve as the base for electoral redistricting. "Census Blocks" are the smallest geographic unit for population data, which form the raw material for redistricting. The process of redistricting involves grouping Census Blocks so the resulting district total populations are equal as defined above. This is the process of creating Redistricting Plan Maps.

Vermont Law Title 17 Elections, Sec 1903(b) provides guidance on how to group Census blocks into districts for the State Legislature. Common sense dictates that municipal redistricting should follow the same.

Sec 1903(b): The representative and senatorial districts shall be formed consistent with the following policies insofar as practicable:

1. preservation of existing political subdivision lines;
    
2. recognition and maintenance of patterns of geography, social interaction, trade, political ties, and common interests;
    
3. use of compact and contiguous territory.

Political Subdivision Lines: Town, City or Ward boundaries. State districts should attempt to follow municipal ward boundaries where possible.

Patterns of Geography, Social Interaction, Common Interests, etc: Includes neighborhoods.

Compactness: A tight geometric shape. A circle is the most compact shape. Contorted shapes have little compactness.

Contiguity: A single unbroken shape. A district divided into two separate pieces is not contiguous. A district divided into two separate pieces touching only at their corners is also not contiguous.

Determining the size of the legislative body (City Council) is the recommended first step in the mapping process.

Table 2: City Council Size and Population Represented

Tradeoffs:

Redistricting guidance criteria are not necessarily complementary, and often adversely affect one another. For example, if a certain neighborhood's geography is not compact, then a compact district may divide the neighborhood into pieces. Conversely, to include all of the non-compact neighborhood in a district, contiguity may have to be less than desired.

Decisions on how to balance tradeoffs between competing goals make redistricting a challenging task. Often there is no best plan, but rather a number of redistricting plan options with differing tradeoffs.

Geographic features may severely limit redistricting options, such as mountain ranges or areas accessible by few roads. For this reason the courts may allow district plans where the Overall Plan Deviation exceeds the 10% maximum limit for equality.