Analyzing the new North Carolina map from a nonpartisan perspective

The North Carolina General Assembly recently passed a new Congressional district map. While it happened, I was following very regular and map-filled updates on the topic from Stephen Wolf, a Daily Kos elections expert. He has done a partisan analysis of the map, forecasting a likely 8–5 split.

The map passed by the NC GA, which will be in effect for the upcoming 2020 congressional elections.

Constellations of counties

The districts are based on counties, which — as objective pre-existing political subdivisions — makes logical sense. A majority of counties are kept as intact as possible, which is a feature of this map that differentiates it from many egregious gerrymanders seen in North Carolina in the past. If we draw each district as a constellation of counties, we get an interesting picture of the choices made by the Republican state legislature.

Counties that are divided as little as possible are marked with solid dots. Counties divided between districts are connected to both districts with dim lines. It may be difficult to see the portions of Catawba and Iredell counties that are excluded from District 10 in the left-hand map.

The geography of the districts

If we superimpose the districts over maps showing the physical geography of the state, it very quickly becomes clear that the districts are not grouped on the basis of the natural geographic divisions of the state.

District constellations over river basins — which historically naturally linked communities, and continues to link their ecological interests.
District “constellations” overlaid on an ecological map of North Carolina from here.

Is this map a gerrymander?

A gerrymander is a division of political districts that deliberately favors one political party over another. In this case, this is a map that could easily elect 8 Republicans and 5 Democrats in an election where Democrats earn a majority of the vote, and displays a number of oddities. Those oddities cannot be explained by attempts to keep together regions of the state with common regional interests, which strongly suggests that the oddities are politically motivated.

A county-level perspective on the districts built from the Charlotte suburbs.

What’s good about this map?

There are several things about this map that are objectively better than many previous maps. I will talk about two non-partisan factors and then explore the partisan factor.

Maps in effect for 2002 elections (left, drawn by Democrats) and 2012 elections (right, drawn by Republicans).
The author’s own attempt at roughing out a fair map based on whole counties. Boundaries would require minor further adjustments.

Looking to the future

Whatever map is in place will only be in effect for a single election cycle, and Democrats could take control of one or both chambers of the North Carolina state legislature in 2020. In addition to the continued shifts in population between the counties, North Carolina is likely to gain an additional district in reapportionment following the census of 2020 due to population growth.

Dr. Tomas McIntee is a mathematician and occasional social scientist with stray degrees in physics and philosophy.

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