Abstract
Partisan gerrymandering poses a threat to democracy. Moreover, the complexity of the districting task may exceed human capacities. One potential solution is using computational models to automate the districting process by optimizing objective and open criteria, such as how spatially compact districts are. We formulated one such model that minimised pairwise distance between voters within a district. Using US Census Bureau data, we confirmed our prediction that the difference in compactness between the computed and actual districts would be greatest for states that are large and, therefore, difficult for humans to properly district given their limited capacities. The computed solutions highlighted differences in how humans and machines solve this task with machine solutions more fully optimised and displaying emergent properties not evident in human solutions. These results suggest a division of labour in which humans debate and formulate districting criteria whereas machines optimise the criteria to draw the district boundaries. We discuss how criteria can be expanded beyond notions of compactness to include other factors, such as respecting municipal boundaries, historic communities, and relevant legislation.
Highlights
One of the greatest threats to democracy, in the USA, is gerrymandering
The results confirmed our prediction that larger states would tend to show greater improvement, suggesting that the complexity of the districting task may overwhelm humans’ ability to find optimal solutions
One startling conclusion is that some of what we view as purposeful gerrymandering may reflect human cognitive limitations
Summary
One of the greatest threats to democracy, in the USA, is gerrymandering. Gerrymandering is the practice of (re)drawing electoral district boundaries to advance the interests of the controlling political faction. Gerrymandering leads to districts with unnecessarily visually complex shapes, e.g. North Carolina (see Fig. 3c). There are laws (both at the state and federal levels) to safeguard the rights of citizens (including minorities) during the redistricting process, in practice these laws do little to reduce partisan gerrymandering [15]. Gerrymandering is on the rise [25] due to partisan actions of both Republicans and Democrats [5]. In the 17 states where Republicans controlled the redistricting process, they secured 72% of the available seats on only 52% of the vote. In the six states where Democrats controlled the districting process, they secured 71% of the seats on 56% of the vote
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