Here's the place for explanations of DistrictBuilder's mapping metrics and how to enter the competition.
About the data and mapping targets:
DistrictBuilder uses 2010 United States Census data and 2017 voter registration data.
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: This is subjective, and will not be a judging feature unless the mapper states that it was a top priority that they attempted to reflect on their map. 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 a 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. Because it is subjective, it will not be a judging feature unless the mapper explicitly states that it was a top priority that they attempted to reflect on their map.
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 2018 competition
How did our previous contestants do? This will give you an idea of targets to hit for your mapping values.
Majority/Minority districts: 1% of maps had zero. 22% had one. The rest had two.
Compactness: Median = 32.7%. Highest = 50.0%. Lowest = 11.9%
Understanding jurisdictional splits
The Pennsylvania State Constitution states that “Unless absolutely necessary no county, city, incorporated town, borough, township or ward shall be divided in forming… a district.”
DistrictBuilder measures county splits, but due to computing limitations, they are not automatically tabulated like the other metrics. Instead, to see your splits, go into “District Tools,” the second tab on the task bar above the map. You can see which counties are split by selecting “Show Splits.” Counties that are split are then highlighted in blue. To see the total number of splits, select “Generate Splits Report.” Click Generate Report at the bottom of the pop-up. This gives you a district-by-district read out of which counties are split by this district, and your total splits at the top of the report.
If this is a metric you value, your goal should be to keep this as low as possible.
Why we don't measure jurisdictional 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. Ultimately, we agree with the reform proposal 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.
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.
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.
Draw the Lines has a wealth of resources to help you out, including our crowd-sourced Hometown Portrait project and our community user forum to connect you with resources to map the entire commonwealth.
We recommend creating an email address (like Google) for each classroom that will be drawing a map. That email address can be tied to multiple usernames and passwords if you are breaking the classroom into smaller teams.
Yes, anyone is welcome to draw their map. However, the competition is only open to Pennsylvania residents.