【摘要】 大客户具有较强的议价能力，客户集中度风险是企业风险管理的重要内容。以往的研究主要集中于客户集中度过高对股票市场的影响，较少关注债券市场中评级机构对发行人大客户风险的甄别能力。本文以2007～2019年发行公司债为样本，检验了债券信用评级对客户集中度风险的揭示程度。实证研究发现：客户集中度越高，信用评级机构的评级等级越低，并带来了更高的信用利差；相比发行人付费评级，投资人付费的独立评级对高客户集中度公司的评级水平相对更低，对大客户风险的甄别效果更好。进一步研究发现，两类评级模式对大客户风险甄别效果的差异在应收账款周转更慢、盈余管理程度更高的企业中表现得更明显；两类评级模式对于国有企业大客户风险的甄别效果均较弱。本文的研究结果表明，债券信用评级市场基本能反映大客户风险，但发行人付费评级模式下对大客户风险还存在一定的虚高评级，应鼓励投资人付费信用评级的发展，促进信用评级体系的有序竞争。更多还原

【Abstract】 As the invisible resources of enterprises, big customers have high bargaining power,and their customer concentration risk becomes an important link of enterprise risk management.Previous studies mainly focused on the impact of excessive customer concentration on the stock market, and paid little attention to the rating agencies’ ability to identify the risk of issuers’ clients in the bond market. Taking corporate bonds issued from 2007 to 2019 as samples, this paper examines the extent to which bond credit rating reveals the risk of customer concentration.Empirical research shows that the higher the customer concentration, the lower the rating of credit rating agencies, and bring higher credit spreads; Compared with issuer paid rating, investor-paid independent rating has a lower rating level for companies with high customer concentration risk and a better screening effect for large customer risk. Further research shows that the difference between the two types of rating agencies is more obvious in the enterprises with slower accounts receivable turnover and higher earnings management degree. The screening effect of the two ratings on the risk of large customers of state-owned enterprises is poor. The research results of this paper show that the bond credit rating market can basically reflect the risk of big customers,but there is still a certain inflated rating for the risk of big customers under the issuer paid rating model. The development of investor paid credit rating should be encouraged to promote the orderly competition of credit rating system.更多还原