This paper provides evidence for why individuals join unions instead of free riding. I model membership as legal insurance. To test the model, I use the incidence of news stories concerning allegations against teachers in the United Kingdom as a plausibly exogenous shock to demand for such insurance. I find that for every five stories occurring in a region, teachers are 2.2 percentage points more likely to be members in the subsequent year. These effects are larger when teachers share characteristics with the news story and can explain 45% of the growth in teacher union membership between 1992 and 2010.

中文翻译：

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工会为何生存：了解工会如何克服搭便车问题

本文提供了为什么个人为什么加入工会而不是自由骑行的证据。我将会员资格建模为法律保险。为了测试该模型，我将有关英国教师指控的新闻报道的发生视为对此类保险需求的外在冲击。我发现，在该地区发生的每五个故事中，第二年出现教师的可能性就高2.2个百分点。当教师与新闻故事共享特征时，这些影响会更大，并且可以解释1992年至2010年之间教师工会会员人数增长的45％。