Results of instrumental variable analysis.

Drawing on the panel data of 284 prefecture-level cities in China spanning from 2011 to 2022, this study empirically examines the impact and underlying mechanisms of population aging on urban income disparities through regression analysis. Additionally, it delves into the moderating role of digital finance in this relationship. The main conclusions are as follows: firstly, population aging has asignificant positive impact on both intra-urban income gap and inter-urban income gap. The heterogeneity analysis indicate that the impact of population aging on the inter-urban income gap cities is more significant in the samples of underdeveloped cities and resource-based cities. Secondly, population aging reduces the labor income share and increases social security expenditure, thus expanding the intra-urban income gap. Meanwhile, population aging enlarges the inter-urban income gap by reducing the technological innovation and impeding industrial structure upgrading. Finally, digital finance effectively alleviates the impact of population aging on the intra-urban income gap and inter-urban income gap. Further research reveals that as the quantile of the intra-urban income gap rises, the marginal impact effect of population aging on intra-urban income gap generally demonstrates a trend of first rising and then declining. Meanwhile, as the quantile of the inter-urban income gap increases, the impact coefficient of population aging on the inter-urban gap tends to decline monotonically.本研究基于2011-2022年中国284个地级市（prefecture-level cities）的面板数据（panel data），通过回归分析（regression analysis）实证检验了人口老龄化（population aging）对城市收入差距（urban income disparities）的影响及其内在作用机制。此外，本研究还深入探讨了数字金融（digital finance）在该关系中的调节作用。 主要结论如下：其一，人口老龄化对城市内部收入差距（intra-urban income gap）与城市间收入差距（inter-urban income gap）均具有显著的正向影响。异质性分析（heterogeneity analysis）结果显示，在欠发达城市（underdeveloped cities）与资源型城市（resource-based cities）的样本中，人口老龄化对城市间收入差距的影响更为显著。其二，人口老龄化通过降低劳动收入占比（labor income share）、增加社会保障支出（social security expenditure），进而扩大了城市内部收入差距；同时，人口老龄化还通过抑制技术创新（technological innovation）与阻碍产业结构升级（industrial structure upgrading），进一步拉大了城市间收入差距。其三，数字金融可有效缓解人口老龄化对城市内部收入差距及城市间收入差距的扩大效应。进一步研究表明，随着城市内部收入差距分位数（quantile）的提升，人口老龄化对城市内部收入差距的边际影响效应整体呈现先升后降的趋势；与此同时，随着城市间收入差距分位数的提升，人口老龄化对城市间收入差距的影响系数呈现单调递减的趋势。