Quantifying Gerrymandering in North Carolina
Quantifying Gerrymandering in North Carolina
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DOI：
10.1080/2330443x.2020.1796400
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发表时间：
2020-08-25
影响因子：
1.6
通讯作者：
Mattingly, Jonathan C.
中科院分区：
文献类型：
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作者：
Herschlag, Gregory;Kang, Han Sung;Mattingly, Jonathan C.
通过将特定的重新划分计划与计划整体进行比较，我们评估该计划是否以公正的方式将个人投票转化为选举结果。明确地，我们评估给定的重新划分计划是否表现出极端的统计属性，而不是满足所有法律标准的非党派计划的合奏。因此，我们捕捉了公正的重新分配计划如何通过州的地理政治景观来解释个人投票。我们通过Markov Chain Monte Carlo算法以及基于不包括党派标准的参考分布的模拟退火来生成计划的合奏。使用合奏和历史投票数据，我们为各种选举结果创建了无零假设，该结果没有党派，这是该州的地理政治。我们展示了北卡罗来纳州最近两个国会区计划的方法，以及由两党退休法官小组制定的计划。我们发现，颁布的计划是极端的离群值，而两党法官的计划并未引起极端的党派成果。同样重要的是，我们通过制定图形表示，以帮助识别和理解与Gerrymandering相关的破裂和包装实例，从而在感兴趣的计划中阐明了异常结构。这些方法在最近的法院案件中成功使用。本文的补充材料可在线获得。
By comparing a specific redistricting plan to an ensemble of plans, we evaluate whether the plan translates individual votes to election outcomes in an unbiased fashion. Explicitly, we evaluate if a given redistricting plan exhibits extreme statistical properties compared to an ensemble of nonpartisan plans satisfying all legal criteria. Thus, we capture how unbiased redistricting plans interpret individual votes via a state's geo-political landscape. We generate the ensemble of plans through a Markov chain Monte Carlo algorithm coupled with simulated annealing based on a reference distribution that does not include partisan criteria. Using the ensemble and historical voting data, we create a null hypothesis for various election results, free from partisanship, accounting for the state's geo-politics. We showcase our methods on two recent congressional districting plans of NC, along with a plan drawn by a bipartisan panel of retired judges. We find the enacted plans are extreme outliers whereas the bipartisan judges' plan does not give rise to extreme partisan outcomes. Equally important, we illuminate anomalous structures in the plans of interest by developing graphical representations which help identify and understand instances of cracking and packing associated with gerrymandering. These methods were successfully used in recent court cases. Supplementary materials for this article are available online.