Baumgartner Frank R, Box-Steffensmeier Janet M, Campbell Benjamin W
Department of Political Science, UNC-Chapel Hill, 313 Hamilton Hall, Chapel Hill, NC, 27599-3265, United States of America.
Department of Political Science, The Ohio State University, 230 North Oval Mall, Columbus, OH 43210, United States of America.
PLoS One. 2018 Jan 2;13(1):e0190244. doi: 10.1371/journal.pone.0190244. eCollection 2018.
Since 1976, the United States has seen over 1,400 judicial executions, and these have been highly concentrated in only a few states and counties. The number of executions across counties appears to fit a stretched distribution. These distributions are typically reflective of self-reinforcing processes where the probability of observing an event increases for each previous event. To examine these processes, we employ two-pronged empirical strategy. First, we utilize bootstrapped Kolmogorov-Smirnov tests to determine whether the pattern of executions reflect a stretched distribution, and confirm that they do. Second, we test for event-dependence using the Conditional Frailty Model. Our tests estimate the monthly hazard of an execution in a given county, accounting for the number of previous executions, homicides, poverty, and population demographics. Controlling for other factors, we find that the number of prior executions in a county increases the probability of the next execution and accelerates its timing. Once a jurisdiction goes down a given path, the path becomes self-reinforcing, causing the counties to separate out into those never executing (the vast majority of counties) and those which use the punishment frequently. This finding is of great legal and normative concern, and ultimately, may not be consistent with the equal protection clause of the U.S. Constitution.
自1976年以来，美国已进行了1400多次司法处决，而且这些处决高度集中在少数几个州和县。各县的处决数量似乎符合拉长分布。这些分布通常反映了自我强化过程，即每次之前发生的事件都会增加观察到另一事件的概率。为了研究这些过程，我们采用了双管齐下的实证策略。首先，我们使用自抽样法进行柯尔莫哥洛夫-斯米尔诺夫检验，以确定处决模式是否反映拉长分布，并证实确实如此。其次，我们使用条件脆弱模型检验事件依赖性。我们的检验估计了给定县每月执行处决的风险，同时考虑了之前的处决数量、凶杀案、贫困情况和人口统计数据。在控制其他因素的情况下，我们发现一个县之前的处决数量会增加下一次处决的概率并加快其时间。一旦一个司法管辖区走上某条特定道路，这条道路就会自我强化，导致各县分化为从未执行处决的县（绝大多数县）和经常使用这种刑罚的县。这一发现引发了重大的法律和规范性问题，最终可能不符合美国宪法的平等保护条款。
