本文采用2007～2012年所有A股上市公司年度报告中披露的前五大销售客户数据，从产品市场和利益相关者的角度，结合我国特有的制度背景，研究了客户集中度对中国上市公司业绩、筹资及投资活动的影响。在理论分析的基础上，本文的实证结果显示，客户集中度越高的企业经营业绩越差；银行贷款的规模越大、期限越长；投资不足的概率和程度越高，研发投入和专利成果越少。以上结果表明，大客户的议价能力越强时会压缩上市公司的利润空间，造成资金压力，从而对银行贷款的需求增加；但优质的客户资源能够发挥声誉传递效应，有助于企业获得银行信贷的支持；最后，由于流动性降低、经营风险增加，客户集中度较高的企业预防性地持有了更多现金，导致投资不足。进一步研究发现，大客户降低了上市公司的毛利率和应收账款周转率，但这种影响取决于企业与客户之间的相对议价能力、企业与客户是否是关联方，以及客户自身的属性；在产能过剩比较严重的行业，大客户能够加速上市公司应收账款和存货的周转速度；由于大客户提高了销售增长率，客户集中度较高的企业市场价值（Tobin’s Q）也越高。此外，优质客户具有声誉传递效应：当前五大客户中上市公司和国有企业的比例越高时，供应商的应收账款和坏账比率显著降低、应收账款周转率和存货周转率显著提高、现金持有水平显著增加，这种声誉效应有助于缓解民营企业的融资约束。而客户集中度对投资行为的影响只在非国有企业和前五大客户均是非关联方时才成立，当企业自身的市场份额越高、前五大客户中上市公司的比例越高时，这种影响被削弱。同时，客户集中度较高的企业整体投资行为趋于保守，其R&D投资和专利产出都显著降低。本文利用中国特有的前五大客户数据，通过区分企业自身与客户的产权性质、企业与客户之间是否为关联方以及客户自身的属性，加深了对供应链客户关系与公司财务行为等相关问题的理解，弥补了现有文献的不足；也为企业改善供应链管理、投资者和债权人利用上下游信息进行决策、监管部门进一步规范非财务信息的披露提供了一定的借鉴。

Using the data of top-five customers disclosed by Chinese listed firms in annual reports between 2007 and 2012 and combining Chinese institutional background, this paper examines the impact of customer concentration on firms’ operating performance, financing activities and investment behaviors from the perspective of product market and stakeholder theory.Based on theoretical analysis, the empirical evidences show that firms with a higher customer concentration have lower ROAs (ROEs), more bank loans, longer loan maturities, more serious under-investment, lower R&D and less patents. These results indicate that the bargaining power of big customers will decrease suppliers’ profits. While superior customers can help suppliers to get more credit supports from banks by transfering their good reputations. Finally, a higher customer concentration will increase the operating risk and decrease liquidity, resulting in a conservative investment decision. Additional analyses find that large customers decrease suppliers’ gross profit margin and turnover of accounts receivables. But this relation relys on the respective bargaining power of suppliers and customers, whether suppliers and customers are related parties and the characteristics of customers. In those industries with overcapacity, large customers can increase the turnover of accounting receivables and inventories. At last, firms with more concentrated customers have higher market values (Tobin’s Q) because of a higher sales growth.Besides, the reputations transferred by customers mainly come from superior customers, such as listed firms and state-owned companies. We find that listed firms and state-owned companies of top-five customers can relieve financial constrains of private firms by reducing suppliers’ account receivables and rate of bad account, speeding the turnover of account receivables and inventories and increasing cash holdings of suppliers. However, the impact of supplier-customer relationships on investment efficiency only exists in private firms and when major customers are non-related parties. Moreover, this impact is weakened in firms with a higher market ratio and more listed firms in top-five customers. Finally, we find that if firms more rely on major customers, they usually have more cautious financial policies. Specifically, they hold more cash and decrease R&D ratios as well as patent outputs. This paper provides new evidences of supplier-customer relationships and deppen the understanding of firms’ financial decisions by distinguishing property rights of suppliers (customers), whether suppliers and customers are related parties and considering characteristics of customers. The main results can help managers to improve supply chain management by optimizing customer structures. They can also help investors and creditors to make decisions by analyzing the detailes of major customers. Finally, we also provide some references for regulators about how to improve the disclosure systems of non-financial information.