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  当前，由于持续的低生育率和不断加剧的人口老龄化，中国人口结构已发生重要转变。加之自新冠肺炎疫情爆发以来，经济下行压力增大，地方财政可持续性面临多重压力。廓清人口在城市间流动的内在动力，并进而解析其对流入地和流出地地方财政可持续性的影响，是一个具有较强理论意义又富有政策含义的话题。一方面，人口流入能为城市创新发展储备一定规模的人力资本，优化劳动力供给结构，进而推动城市经济持续增长；城市人口大量集聚会进一步改变政府税收结构和提升税收规模，增加政府财政收入，有助于地方政府财政的可持续化。另一方面，人口流出会导致流出地税基缩小，人口大量流入也会导致流入地公共服务支出的增加，不利于地方财政可持续性提升。

  本文的研究思路为：首先，基于流入地视角，通过理论模型推导和影响路径分析，将人口流动对地方财政可持续性的影响效应分解为税基效应、集聚效应和拥挤效应，并纳入市场化水平的调节效应。其次，采用2015—2020年中国266个地级市面板数据，在进行现状分析的基础上，运用固定效应模型、调节效应模型和门槛模型，实证分析人口流动对地方财政可持续性的影响，并通过替换核心解释变量和更换回归模型的稳健性检验保证分析结果的可靠性。最后，将样本数据按城市等级和城市规模进行划分，分析人口流动对地方财政可持续性的影响在不同类型城市之间的异质性。

  研究结果表明：（1）人口流动对地方财政可持续性产生显著正向影响，且市场化水平越高，其正向影响越强。这一结论在替换核心解释变量及更换回归模型后仍然成立。（2）门槛回归结果表明，随着人口流动性的增加，人口流动对地方财政可持续性的影响呈现先增强后减弱的倒“U”型特征。（3）基于城市等级的异质性分析结果表明，人口流动对二线和五线城市地方财政可持续性影响显著，对其他等级的城市影响不显著；基于城市规模的异质性分析结果表明，人口流动对大城市和小城市的地方财政可持续性影响显著，而对中等城市的地方财政可持续性影响不显著。

  因此，不同城市应根据其人口流动趋势，制定有针对性的政策。对于人口流入地而言，应努力为流动人口提供良好的就业和生活环境，才能充分享受人口流动带来的益处，进而增加财政收入，提升地方财政可持续性；同时，也应注重提升地方政府公共物品供给效率和治理能力，缓解人口流入导致的拥挤效应。对人口流出地而言，应通过政策倾斜等方式留住人才，避免人口进一步外流；优化产业结构，增加财政收入来源；根据人口流动趋势及时调整公共服务支出，提高各项财政资金的配置效率。各城市可通过提升市场化水平，扩大人口流动的正向效应，减弱其负向效应，以提升财政可持续性，还可通过推动金融发展和数字经济发展提升地方财政可持续性。

  At present, due to the persistent low fertility rate and the increasing aging of the population, the population structure of China has undergone important changes. In addition, since the outbreak of the coronavirus pandemic, the downward pressure on the economy has increased, and the financial sustainability of local governments has faced multiple pressures. It is a topic with strong theoretical and policy significance to clarify the internal motivation of population mobility between cities and then analyze its impact on the local financial sustainability of inflow and outflow areas. On the one hand, population inflow can reserve a certain scale of human capital for urban innovation and development, optimize the labor supply structure, and then promote the sustained growth of urban economy; A large concentration of urban population will further change the government's tax structure and increase the tax scale, increase the government's fiscal revenue, and contribute to the sustainability of local government finance. On the other hand, the outflow of population will lead to the narrowing of the tax base in the outflow area, while the influx of population will also lead to the increase of public service expenditure in the inflow area, which is not conducive to the improvement of local fiscal sustainability.

  The research ideas of this paper are as follows: First, based on the perspective of inflow place, through theoretical model derivation and influence path analysis, the influence effect of population mobility on local fiscal sustainability is decomposed into tax base effect, agglomeration effect and crowding effect, and the adjustment effect of marketization level is considered. Secondly, using the panel data of 266 prefecture-level cities in China from 2015 to 2020, this paper empirically analyzes the impact of population mobility on local fiscal sustainability by using fixed effect model, regulatory effect model and threshold model, and ensures the reliability of the analysis results by replacing the core explanatory variables and the robustness test of the regression model. Finally, the sample data are divided according to city level and city size, and the heterogeneity of the impact of population mobility on local fiscal sustainability among different types of cities is analyzed.

  The results show that: (1) Population mobility has a significant positive impact on the sustainability of local finance, and the higher the level of marketization, the stronger its positive impact. This conclusion still holds after replacing the core explanatory variables and the regression model. (2) The results of threshold regression show that with the increase of population mobility, the impact of population mobility on local fiscal sustainability presents an inverted "U" shape, which first strengthens and then weakens. (3) The results of the heterogeneity analysis based on the city level show that population mobility has a significant impact on the local financial sustainability of second-tier and fifth-tier cities, but has no significant impact on other cities; Based on the heterogeneity analysis of city size, the results show that population migration has a significant impact on the local financial sustainability of big cities and small cities, but has no significant impact on the local financial sustainability of medium-sized cities.

  Therefore, different cities should formulate targeted policies according to their population mobility trends. For the places where the population flows in, efforts should be made to provide a good employment and living environment for the floating population, so that they can retain people and fully enjoy the benefits brought by the population inflow, thereby increasing fiscal revenue and enhancing the sustainability of local finance; At the same time, we should also pay attention to improving the supply efficiency and governance capacity of local governments, and alleviate the crowding effect caused by population inflow. For the population outflow areas, we should adjust the industrial structure in time, increase the sources of fiscal revenue, adjust the public service expenditure in time according to the population flow trend, and improve the allocation efficiency of various financial funds. All cities can improve the financial sustainability by improving the level of marketization, expanding the positive effects of population mobility, weakening its negative effects, and promoting the financial development and digital economy.