Welfare Analysis of Legislative Redistricting

最近最高法院涉及种族和党派划分选区的案件加剧了一场关于立法重新划分选区的全国性辩论。然而，在这场辩论中，对于如何从促进选民利益的角度评估替代重新划分选区的计划，几乎没有达成一致意见。最根本的问题是：立法机关应该如何代表不同的选民群体，选民应该如何在不同的地区分配，以执行这一处方？本项目在传统福利经济学的基础上发展了一种方法，以便从理论和经验的角度解决这一问题和相关问题。作为一个规范性基准，主要调查人员首先检查意识形态团体在立法机构中应该如何代表。关键的发现是，席位-选票曲线，即左翼政党拥有的席位比例与其全国支持率之间的关系，应该是线性的，具有正斜率，并偏向于占主导地位的政党。然后，他们研究选民应该如何在不同地区分配，以实施这一最佳席位-选票曲线。这里的主要发现是，如果最优席位-选票曲线能够实施，那么选区在选民意识形态的分配上应该是不同的，一些选区应该是“安全席位”。最后，该项目将开发实施最佳席位-选票曲线的条件，然后解决当这些条件不满足时应如何在各区分配选民的难题。研究小组还将开发一种综合的理论和经验方法，从这一福利角度评估立法重新划分选区。它首先开发了一种估计席位-选票曲线的方法；这种方法只需要左翼政党在立法选举中逐区支持的数据。研究人员随后证明，选民福利可以根据观察到的席位-选票曲线以及任何其他可能的席位-选票曲线直接衡量。因此，观察到的选民福利可以与最优席位-选票曲线下的选民福利进行比较，从而可以衡量次优重新划分造成的任何福利损失。此外，观察到的选民福利可以与比例代表制下的选民福利进行比较，比例代表制是其他国家普遍使用的另一种投票制度。该方法还允许比较不同选区划分制度下的选民福利，包括两党、党派和独立委员会。最后，这些想法在美国州议会选举的投票申请中得到了说明。第三个项目旨在将前两部分提出的想法推广到一个框架中，在这个框架中，选民和候选人都是由他们的意识形态和种族来界定的。这一概括性框架将用于解决重新划分选区中与种族有关的几个规范性问题。例如，黑人选民在立法机构中应该如何代表，并在不同地区之间进行分配？虽然黑人占多数的选区倾向于选举黑人候选人，但他们也集中了自由派选民，这可能会导致其他选区的左翼候选人落败。因此，我们计划研究种族和意识形态之间的这种和其他潜在的有趣的相互作用。

Recent Supreme Court cases involving both racial and partisan gerrymandering have intensified a national debate over legislative redistricting. There is little agreement, however, in this debate over how alternative redistricting plans should be evaluated from the perspective of promoting the interests of voters. At its most fundamental level, the relevant question is: how should legislatures represent different groups of voters, and how should voters be allocated across districts in order to implement this prescription? This project develops an approach based upon traditional welfare economics in order to address this question and related questions from both a theoretical and empirical perspective. As a normative benchmark, the principal investigators begin by examining how ideological groups should be represented in legislatures. The key findings are that the seats-votes curve, which relates the fraction of seats held by the leftist party to its national support, should be linear, have a positive slope, and be biased in favor of the dominant party. They then examine how voters should be allocated across districts in order to implement this optimal seats-votes curve. The key findings here are that, if the optimal seats-votes curve can be implemented, then districts should be heterogeneous in their allocation of voter ideologies and that some districts should be "safe seats". Finally, the project will develop conditions under which the optimal seats-votes curve can be implemented and then tackle the difficult question of how voters should be allocated across districts when these conditions are not satisfied. The research team will also develop an integrated theoretical and empirical approach to evaluating legislative redistricting from this welfare perspective. It first develops a methodology for estimating seats-votes curves; this methodology requires only data on district-by-district support for the leftist party in legislative elections. The researchers then demonstrate that voter welfare can be directly measured for this observed seats-votes curve as well as for any other possible seats-votes curve. Thus, observed voter welfare can be compared with voter welfare under the optimal seats-votes curve, permitting measurement of any welfare losses from sub-optimal redistricting. In addition, observed voter welfare can be compared with voter welfare under proportional representation, an alternative voting system commonly used in other countries. The methodology also permits a comparison of voter welfare under alternative redistricting regimes, including bipartisan, partisan, and independent commissions. Finally, these ideas are illustrated in an application to voting in U.S. state legislative elections. The third project aims to generalize the ideas developed in the first two parts to a framework in which both voters and candidates are defined by their ideology as well as by their race. This generalized framework will be used address several normative questions related to race in redistricting. For example, how should black voters be represented in legislatures and allocated across districts? While black majority districts tend to elect black candidates, they also concentrate liberal voters, potentially leading to the defeat of leftist candidates in other districts. Thus, we plan to examine this and other potentially interesting interactions between race and ideology.