Using an ensemble of redistricting plans, we evaluate whether a given
political districting faithfully represents the geo-political landscape.
Redistricting plans are sampled by a Monte Carlo algorithm from a probability
distribution that adheres to realistic and non-partisan criteria. Using the
sampled redistricting plans and historical voting data, we produce an ensemble
of elections that reveal geo-political structure within the state. We showcase
our methods on the two most recent districtings of NC for the U.S. House of
Representatives, as well as a plan drawn by a bipartisan redistricting panel.
We find the two state enacted plans are highly atypical outliers whereas the
bipartisan plan accurately represents the ensemble both in partisan outcome and
in the fine scale structure of district-level results.