Abstract:    Enterprise innovation is the main driving force of building an innovative country, but the financing constraint faced by enterprises has been a bottleneck affecting their R&D activities. How to alleviate the financing constraint of enterprise innovation activities has been a major problem in both practical and theoretical circles. However, due to the inherent characteristics of innovation such as high investment, high risk and high uncertainty, the spillover of innovation results and the asymmetry of innovation information make corporate innovation often face serious financing constraints. In particular, the disruption of local and global supply chains brought about by the COVID-19 epidemic poses a serious challenge to the development of firms′ production and innovation activities. However, the existing literature has mainly explored the factors influencing the financing constraints faced by firms′ innovation activities based on the macro level (Wan et al., 2020; Tang and Wu, 2015), but rarely explores the impact of customer earnings performance on the financing constraints of firm innovation from a supply chain information spillover perspective.In view of this, this research examined the impact of customer earnings performance on firms′ innovation financing constraints based on the guarantee effect and signaling effect of high-earning customers using manually collated supply chain data from 2009-2018 for 1389 pairs of customers and firms that are both listed companies. It was found that the better the customer earnings performance, the more it helps to alleviate the financing constraint of corporate innovation. Among them, the high earning customer guarantee effect and signaling effect help expand the scale of debt financing and equity financing of enterprises, which in turn effectively alleviate the financing constraints faced by enterprises′ innovation activities. In addition, when the supply chain relationship is more stable and benign, and the geographical proximity of large customers is more proximate, the stronger the role of customer earnings performance in alleviating enterprises′ innovation financing constraints. Further analysis found that the role of customer earnings performance in reducing firms′ innovation financing constraints is particularly significant when non-state enterprises and economic policy uncertainty are high.The contributions of this research are as follows. First, it has expanded the research boundary of the economic consequences of customer earnings performance. The current literature mainly explored the effects of customer earnings information spillovers on corporate stock prices, bank loan maturities, and investment efficiency (Peng and Wang, 2018; Kim et al., 2015; Chen et al., 2021), but rarely explored how customer earnings performance affects the financing constraints of firm innovation from a supply chain relationship perspective. This paper showed that customer earnings performance is an important factor affecting the financing constraint of corporate innovation. Second, it has provided empirical evidence on the channels of the role of customer earnings performance in alleviating firms′ innovation financing constraints. The current literature mostly directly examined the relationship between customer characteristics such as government background customers, stable customers and firm innovation (Dou et al., 2020; Qiu and Cheng, 2021), lack of analysis of its mechanism of action. This paper analyzed and verified that customer earnings performance can effectively alleviate the financing constraints of corporate innovation by increasing the scale of corporate debt and equity financing. Third, this paper has expanded the depth of research on the impact of customer earnings performance on enterprise innovation financing constraints from the perspective of supply chain relationships, and confirmed that the establishment of stable and benign supply chain relationships can help enterprise innovation financing activities, which has provided empirical evidence for the current policy of "improving the stability and competitiveness of industrial chain supply chains".According to the findings of this paper, the following main insights are drawn: (1) For enterprises, they should actively build strong ties with high quality customers to effectively alleviate the financing constraints of corporate innovation. At the same time, enterprises should establish long-term stable and benign supply chain relationships with high-earning customers. In addition, enterprises can make use of the geographical location advantage to optimize the supply chain system, strengthen the information exchange with customers in the geographical proximity, and create a good supply chain ecology. (2) For creditors such as banks, when evaluating the innovative investment decisions of enterprises, they can combine with the earnings performance of customers to adjust the scale of enterprise loans and reduce credit risks in a timely manner. For investors such as shareholders, they need to strengthen their understanding of the spillover effect of customer information in supply chain relationships. Investors should review the situation to adjust their investment decisions. (3) For the government, the regulator should regulate the public information disclosure of enterprises and effectively improve the authenticity and effectiveness of information disclosure. In addition, in the current environment of high political and economic uncertainty, the government should facilitate financing from banks and other financial institutions for enterprises, especially non-state enterprises, in order to broaden their financing channels, reduce financing costs, and promote their enthusiasm for investing in innovative activities.

Key words: customer earnings performance, financing constraint, innovation, supply chain relationship, geographical proximity of customers