In this article, we use panel data from 457 listed banks in 20 countries to investigate the impact of bank liquidity hoarding on systemic risk in the banking sector and discuss it under the condition of economic policy uncertainty (EPU). Empirical evidence suggests that when banks' liquidity hoarding increases, their systemic risk contribution decreases significantly. Furthermore, we demonstrate that bank liquidity hoarding works through the channel of improving bank operational stability and reducing bank asset risk. In addition, during a period of high EPU, bank liquidity hoarding has a more significant effect on reducing systemic risk. Our results remain stable after a battery of robustness checks. Heterogeneity analysis indicates that the role of bank liquidity hoarding in reducing systemic risk is more significant in larger banks and banks in developed countries. Moreover, this effect is particularly pronounced when there is an accommodative monetary policy environment. Our study has some important implications for policymakers and regulators. Previous research suggests that policymakers may consider encouraging the banking sector to actively create liquidity instead of hoarding it, as this could lead to higher economic output. However, from the perspective of financial stability, banks' liquidity hoarding can help reduce their systemic risk contribution, especially in periods of high external uncertainty. Therefore, policymakers need to evaluate bank liquidity hoarding behaviour more comprehensively, and strike a balance between promoting economic growth and ensuring financial system stability to maximize overall welfare.

在本文中，我们利用20个国家457家上市银行的面板数据来考察银行流动性囤积对银行业系统性风险的影响，并在经济政策不确定性（EPU）条件下进行讨论。经验证据表明，当银行流动性囤积增加时，其系统性风险贡献显着下降。此外，我们证明银行流动性囤积是通过提高银行运营稳定性和降低银行资产风险的渠道发挥作用的。此外，在EPU较高时期，银行流动性囤积对于降低系统性风险的作用更为显着。经过一系列稳健性检查后，我们的结果保持稳定。异质性分析表明，银行流动性囤积对降低系统性风险的作用在规模较大的银行和发达国家银行中更为显着。此外，在宽松的货币政策环境下，这种效应尤其明显。我们的研究对政策制定者和监管者有一些重要的影响。此前的研究表明，政策制定者可能会考虑鼓励银行业积极创造流动性而不是囤积流动性，因为这可能会带来更高的经济产出。然而，从金融稳定的角度来看，银行囤积流动性有助于降低其系统性风险贡献，尤其是在外部高度不确定的时期。因此，政策制定者需要更全面地评估银行流动性囤积行为，在促进经济增长和确保金融体系稳定之间取得平衡，实现整体福利最大化。