for helpful comments, We thanked ran Abramitzky, Abhishek Arora, Leh Boustan, Leo Bursztyn, Martin Fiszbein, Vicky Fouka, Ed Glaeser, Grant Goehring, Claudia Goldin, Stefan Heblich, Pat Kline, bob Margo, Sendil Mullanathan, Hong Wang, David Yanagizawa-Drott, Noam Yuchtman和研讨会/会议/会议参与者在BU,Brown,Chicago,Cuhk深圳,哈佛大学,牛津,慕尼黑,NBER SUMMER Institute,Stanford,Warwick和Eth-Zurich举行。for outstanding research assistance, we thankstand lidia Barski, Augustus Balocher-Rubin, Catrina Brown, Vikram Dixit, Shreya Dutt, Ella Edmond, Soala Ekine, Giacomo Gattorno, Danile Gofffi, Mashod Harrison, Annie Herring, Justin Johnson, Angeli Kini, Dahlia Levine, Shraddha Mandi, Isaac while,盗窃Polyak,Simone Seiner,Elijah Sumernikov,Mafo Tekobo和Hans Xu。 所有潜在的错误都是我们自己的。 我们没有相关的财务关系披露。 本文所表达的观点是作者的观点,不必反映国家经济研究局的观点。for outstanding research assistance, we thankstand lidia Barski, Augustus Balocher-Rubin, Catrina Brown, Vikram Dixit, Shreya Dutt, Ella Edmond, Soala Ekine, Giacomo Gattorno, Danile Gofffi, Mashod Harrison, Annie Herring, Justin Johnson, Angeli Kini, Dahlia Levine, Shraddha Mandi, Isaac while,盗窃Polyak,Simone Seiner,Elijah Sumernikov,Mafo Tekobo和Hans Xu。所有潜在的错误都是我们自己的。我们没有相关的财务关系披露。本文所表达的观点是作者的观点,不必反映国家经济研究局的观点。