Political actors frequently manipulate redistricting plans to gain electoral advantages, a process commonly known as gerrymandering. To address this problem, several states have implemented institutional reforms including the establishment of map-drawing commissions. It is difficult to assess the impact of such reforms because each state structures bundles of complex rules in different ways. We propose to model redistricting processes as a sequential game. The equilibrium solution to the game summarizes multi-step institutional interactions as a single dimensional score. This score measures the leeway political actors have over the partisan lean of the final plan. Using a differences-in-differences design, we demonstrate that reforms reduce partisan bias and increase competitiveness when they constrain partisan actors. We perform a counterfactual policy analysis to estimate the partisan effects of enacting recent institutional reforms nationwide. We find that instituting redistricting commissions generally reduces the current Republican advantage, but Michigan-style reforms would yield a much greater pro-Democratic effect than types of redistricting commissions adopted in Ohio and New York.

翻译：政治行为者经常操纵选区重划方案以获取选举优势，这一过程通常被称为不公正划分选区。为解决此问题，多个州已实施包括设立地图绘制委员会在内的制度改革。由于各州以不同方式构建了复杂的规则组合，评估此类改革的影响十分困难。我们提出将选区重划过程建模为序贯博弈。该博弈的均衡解将多步骤制度互动概括为单一维度评分。该评分衡量政治行为者对最终方案党派倾向的操纵空间。通过采用双重差分设计，我们证明当改革约束党派行为者时，能够减少党派偏见并提升竞争性。我们进行了反事实政策分析，以评估在全国范围内实施近期制度改革可能产生的党派效应。研究发现，设立选区重划委员会通常会削弱当前共和党的优势，但密歇根式改革将产生远比俄亥俄州和纽约州采用的选区重划委员会类型更大的亲民主党效应。