Abstract: As an important supplement to formal agreements and institutional arrangements，the establishment of international twin cities has strengthened trust and indepth communication between cities，becoming an important catalyst and booster for international economic cooperationBased on the perspective of foreign trade highquality development，this paper examines the impact of the“circle of friends”formed by international twin cities on the export trade between cities using the data of matching pairs between 287 Chinese cities and 136 countries or regions in 20022015The results find that： （1）The agreements of international twin cities have significantly promoted the export volume and export value of Chinese cities by 100% and 116% respectively（2）The trade promotion effect of international twin cities is more derived from trade creation rather than trade transfer（3）In addition to affecting exports by intensive margins，international twin cities have also promoted the expansion margins of exports in terms of the number of product types and the proportion of hightech industries（4）With SARS and the global financial crisis as incident impacts，the agreements of international twin cities has strengthened the ability of Chinese cities to resist risks in exports（5）The results of heterogeneity analysis show that the agreements of international twin cities have more obvious export promotion effect on nonBelt and Road countries and geographically adjacent countries in ChinaThe above results are supported by a series of robustness testsThis paper is of great value to comprehensively understand the economic connotation of international twin cities and to explore new paths for highquality development of international trade

Key words:  , international twin cities； export promotion effects； informal institutions； risk resistance； dual margins

摘要： 作为正式协议和制度安排的重要补充，缔结国际友好城市关系加强了中外城市之间的信任和深层次交流，成为国际经济合作的重要催化剂和助推器。本文从外贸高质量发展视角切入，基于2002—2015年287个中国城市与136个国家或地区的匹配对数据，考察了国际友好城市形成的“朋友圈”是否以及如何影响城市间的出口贸易。研究发现：（1）缔结国际友好城市协议使得中国城市出口量和出口额分别提高了100%和116%。（2）国际友好城市的贸易促进效应更多源于贸易创造而非贸易转移。（3）除了影响出口集约边际，国际友好城市还从产品种类数和高技术行业所占比例等方面促进了出口扩展边际。（4）以非典和全球金融危机作为事件冲击，国际友好城市协议在一定程度上增强了中国城市出口的风险抵抗能力。（5）异质性分析结果表明，国际友好城市协议对非“一带一路”倡议国家与地理邻近国家或地区的出口促进效应更明显。以上结果得到了一系列稳健性检验的支持。本文的研究有助于全面认识国际友好城市的经济内涵以及探讨外贸高质量发展的新路径。

关键词: 国际友好城市, 出口促进效应, 非正式制度, 风险抵抗, 二元边际