The COVID-19 epidemic upended social and economic life in the United States. To reduce transmission, people altered their mobility and interpersonal contact, and state and local governments acted to induce social distancing through across-the-board policies. The epidemic and the subsequent social distancing response led to high unemployment and to efforts to reopen the economy using more-targeted virus mitigation policies.

This paper makes five contributions to studying epidemic policy and mobility. First, we review COVID-19 research on mobility, labor markets, consumer behavior, and health. Second, we sketch a simple model of incentives and constraints facing individuals. Third, we propose a typology of government social distancing policies. Fourth, we review new databases measuring cellular mobility and contact. Fifth, we present regression evidence to help disentangle private versus policy-induced changes in mobility.

During the shutdown phase, large declines in mobility occurred before states adopted stay-at-home (SAH) mandates and in states that never adopted them, suggesting that much of the decline was a private response to the risk of infection. Similarly, in the reopening phase mobility increased rapidly, mostly preceding official state reopenings, with policies explaining almost none of the increase.

COVID-19流行病改变了美国的社会和经济生活。为了减少传播，人们改变了他们的流动性和人与人之间的联系，州和地方政府采取了通过全面政策诱使社会疏远的行为。流行病和随之而来的社会疏远反应导致高失业率，并致力使用针对性更强的病毒缓解政策来重新开放经济。

本文为研究流行病政策和流动性做出了五点贡献。首先，我们回顾一下COVID-19关于流动性，劳动力市场，消费者行为和健康的研究。其次，我们勾画出个人面临的激励和约束的简单模型。第三，我们提出了政府社会疏远政策的类型。第四，我们回顾了测量细胞流动性和接触性的新数据库。第五，我们提供了回归证据，以帮助区分私人与政策引起的流动性变化。

在关闭阶段，流动性大幅度下降是在各州采用“不在家”（SAH）强制性规定之前，以及从未采用过这些规定的各州，这表明这种下降的很大一部分是私人对感染风险的反应。同样，在重新开放阶段，流动性迅速增加，大多是在官方国家重新开放之前进行的，政策几乎没有说明增加的原因。