About the data and mapping targets:

  • DistrictBuilder uses 2010 United States Census data and 2017 voter registration data. 

  • To enter the mapping competition, you must create 17 districts. Why 17? Because this contest simulates what will happen when PA likely loses a seat after the 2020 Census. DistrictBuilder also offers the ability to draw a starter map, where you can start with 13-14 districts already completed and finish up the last 3-4.

  • Target Population: All 17 districts must have a population between 743,463 and 750,935 for the map to be valid. This is +/- 0.5% of the exact target population, 747,199.

  • Contiguous: All 17 districts must be contiguous (represented by a green check mark).

  • Competitiveness: We considered a district that has a 10%-or-less difference between registered Democrats and registered Republicans to be competitive.

  • Majority-Minority districts: There is not an explicitly required number of districts that Pennsylvania needs in which the majority of its population is comprised of people of color. However, the Voting Rights Act of 1965 protects minority groups from having the power of their vote diluted, so that they can have regular and meaningful opportunities to elect a candidate of their choice. DistrictBuilder defines a majority-minority district as one in which people who are nonwhite ethnicities are in the majority. In Pennsylvania, this generally works out to two districts in the Philadelphia area.

  • Compactness: The higher the percentage, the better, for those mappers valuing compactness. DistrictBuilder uses the Polsby-Popper method for determining compactness. Read more about it here.

  • Population Equivalence: Your goal is - 0 -. This measures the difference between your smallest district and your largest. It helps demonstrate your skill in getting your populations as equal as possible.

  • County splits: If this is a measurement you valued, then the fewer, the better. This is the number of times a county is split into two or more districts. Read more about jurisdictional splits below.

Scores from the fall 2019 competition

How did our previous contestants do? This will give you an idea of targets to hit for your mapping values.

  • Competitive districts: The median was 9. The lowest was 6, while the highest was 16.
  • Majority/Minority districts: 1% of maps had zero. 22% had one. The rest had two.

  • Compactness: Median = 32.9%. Highest = 47.5%. Lowest = 12.8%. 

  • Population Equivalence: Median: 6,313. Lowest = 496. Highest = 7,461.   If one wanted to score in the top 25%, you'd have to achieve a population equivalence of 5,299. Top 10% = 4,329
  • County Splits: Median = 56. Lowest = 29. Highest = 137

Why we don't measure municipal splits

Because we did not have the time or resources to edit the platform to include municipalities as a geounit, we are unable to measure splits or allow mappers to use them as a geounit to build their map.

However, using the municipality base map and the transparency slider, you can work to minimize those splits yourself, despite their not being a digital measurement for how many you have generated.

Why DistrictBuilder permits population variance that exceeds constitutional limits

According to redistricting expert Justin Levitt: “states must make a good-faith effort to draw districts with exactly the same number of people in each district within the state.” Because DistrictBuilder mappers can’t go below the census tract level, it’s not realistic to expect you to create equally populated districts down to the person. We believe that a 0.5% acceptable range was satisfactory for a demonstration project like DistrictBuilder.

Why we use voter registration data, not election-result data

This was a tough one. We understand the argument that previous election results should not be considered in the creation of future maps. However, we know that some citizen mappers will want to see the political impact their maps would have. So we compromised.

General Questions

What does a DistrictBuilder map need to be valid for the competition?

It needs to meet three criteria: (1) it has 17 total districts; (2) each district falls within +/- 0.5% of the target population (Pennsylvania’s total population divided by our number of congressional districts); and (3) every district is contiguous, meaning it is a single, unbroken shape.

Will these maps be constitutional?

The maps you will draw will reflect the broad principles that define a constitutional map, including compactness, contiguity, equal population, respect for majority-minority districts as required by the Voting Rights Act of 1965, and honoring jurisdictional boundaries. Because mappers are using larger base geounits (census tracts instead of census blocks or voting precincts), these maps are meant for engagement and education, not the kind of precision that would stand up to a legal challenge. Over the next three years, we hope to keep improving the tool. Your feedback can help us do that.

As Draw the Lines and Azavea work together to raise more funds, they aim to build a DistrictBuilder 2.0, which will allow users to build maps that will be fully updated and modernized, along with the use of 2020 Census data.

Is this available to people outside of Pennsylvania?

Yes, anyone is welcome to draw their map. However, the competition is only open to Pennsylvania residents.