Mapping Standards

Standards give redistricting commissions a way to judge maps and provide guardrails against gerrymandering.

Standards include federal requirements, best practices established by legal precedent, and specific measurable mapping criteria. When these are not clearly defined, or if priority order is not clearly established, commissions can focus on some aspects of mapping while ignoring others. Redistricting inevitably consists of value judgements and trade-offs. Well-defined priorities can help prevent litigation and make accurate representation more likely.

A top federally required standard is population equality. For congressional maps this has been interpreted as exact equivalence unless other priorities are applied consistently or required by state law. For state legislative districts, disparities of up to ten percent have been permitted. The proposed legislation would provide specific population deviations for Congressional and PA House and Senate districts.

Another top federal requirement is protection against minority vote dilution. The proposed bill requires compliance with all federal laws, but also says explicitly that a redistricting plan must provide racial minorities an equal opportunity to participate in the political process and may not dilute or diminish their ability to elect candidates of their choice, whether alone or in coalition with others.

Beyond those federal requirements, current PA law requires that districts be compact (avoiding meandering boundaries), contiguous (which means all parts of a district are geographically connected), and divide counties and municipalities as little as possible. Those requirements are often in conflict in Pennsylvania since many municipal boundaries are not compact and some districts and counties are also not completely contiguous.

The proposed legislation would prioritize those standards under a higher goal of partisan fairness. Maps could not be drawn to provide an advantage to an incumbent or a party. Ways to assess this include measures of partisan bias (assessing any built-in advantage for one party) and responsiveness (measuring the extent to which votes cast will be accurately reflected in the number of seats won).

The proposed bill provides limits on how often counties can be split, prohibits dividing precincts, allows for small non-contiguous fragments that reflect non-contiguous counties or municipalities, and requires attention to communities of interest. To the extent possible when those requirements are met, PA districts should also be compact and reflect geographic boundaries.

What about competitiveness?

Competitive districts are often not possible without trampling most other redistricting criteria. Given Pennsylvania’s current partisan composition, prioritizing competitive districts could mean oddly shaped districts dividing multiple communities in an attempt to balance different political parties within individual districts. If drawn according to other prioritized standards, regions that are balanced between both parties should yield competitive districts, and the overall outcome of any legislative election should accurately reflect the current partisan composition of the state. If PA continues to have similar numbers of voters from both major parties, overall district plans should be highly competitive, even when many individual districts are not.


Allocation of incarcerated persons

Other resources: Where Are the Lines Drawn? All About Redistricting, Loyola Law School