Abstract: Social insurance contribution is an important social security mechanism. The Social Insurance Law issued in July 2011 has increased the social insurance contributions of enterprises, causing them to face higher employment costs and lower levels of free cash flow, so that they are forced to find a balance between financial pressure and investment efficiency and adjust their investment decisions. Based on the data of A-share listed companies in China from 2007 to 2021, this paper employs a double difference model to conduct an analysis. The findings show that an increase in social insurance contributions will increase the labor employment cost of enterprises, reduce their disposable cash flow, and lower their investment level. However, at the same time, it also promotes enterprises to improve their production technology level, make prudent investment decisions, and thereby improve their investment efficiency. This effect is more significant in industries with higher competition, registered in the eastern region, or with higher levels of financing constraints, because these enterprises are more sensitive to the financial pressure brought about by the increase in social insurance contributions. Therefore, the social insurance system can achieve the goals of resource allocation and economic regulation to a certain extent by influencing the investment behavior of enterprises. In this institutional context, China should continue to promote tax and fee reduction reform measures, and implement targeted subsidy policies to encourage stable investment by enterprises and improve their investment efficiency. At the same time, corresponding measures should be taken to prevent the systematic risks brought by the excessive financialization of enterprises.

Key words: Social Insurance Law, social insurance contributions, investment level of enterprises, corporate investment efficiency