Comparing two territory partitions in districting problems: Indices and practical issues

Planning as part of public sector decision-making situations is an activity of critical importance, with direct relevance for urban planners. The ramifications of such decisions generally have significant effect on peoples’ lives. The current paper deals with the comparison between territorial maps in the context of districting problems with a strong socio-economic component. The theoretical problem involves the comparison of two partitions in a connected, undirected, and planar graph. In considering this problem, we introduce three new indices to compare territory partitions: compatibility, inclusion, and distance, all of which have importance for real-world planning situations. Numerical experiments of these indices were carried out for the communes network in (Iˆle de France), France.     

Optimal redistricting under geographical constraints: Why “pack and crack” does not work

We show that optimal partisan redistricting with geographical constraints is a computationally intractable (NP-complete) problem. In particular, even when voter's preferences are deterministic, a solution is generally not obtained by concentrating opponent's supporters in “unwinnable” districts (“packing”) and spreading one's own supporters evenly among the other districts in order to produce many slight marginal wins (“cracking”).