美国安然事件爆发后，其审计师安达信会计师事务所声誉严重受损，在此期间安达信的其他审计客户股价大幅下跌，投资者遭受巨大损失。利益相关者如何能够更好的评估审计质量，是学术界和监管机构共同关注的重要问题。当前的研究发现会计师事务所以及分所层面存在财务重述的传染效应，即事务所（或者分所）的一家客户发生财务重述时，该所其他客户的审计质量显著更差。本文利用中国特有的审计师个人信息数据，将财务报表重述的传染效应延伸到审计师个人层面，并分析了审计师个人所承担的经济后果，以及社会关系对审计师个人之间发生传染效应的影响，为研究审计师个人对审计质量的影响方式、经济后果提供了更多的实证证据。具体而言，本文的主要研究结果包括以下三个方面：首先，本文发现了基于审计师个人层面的财务报表重述的传染效应，即客户发生财务报表重述的审计师（简称低质量审计师）所审计的其他客户的财报质量显著低于其他公司。这个结果表明，以往研究所发现的事务所或者分所层面的传染效应源于低质量审计师个人层面的传染效应。进一步的分析显示，该传染效应主要存在于非十大会计师事务所、有限责任公司制会计师事务所，以及审计师个人当年工作负荷较大的子样本中；最后，不同类型的财务报表重述导致传染效应也有所不同。其次，本文发现客户发生财务报表重述后，低质量审计师个人层面的市场份额相比于其他审计师而言有明显的下降，不仅更容易失去原有的审计客户，也更难获取新客户。与这个结果一致，研究显示这些低质量审计师更容易被现有客户换掉，而且在没有发生审计师更换的样本中，低质量审计师获取的审计费用更可能被大幅降低。最后，被低质量审计师所审计的公司年报盈余反应系数在财务报表重述披露当年发生显著下降，但是这种现象只存在于财务报表重述当年，没有延续到之后的年份。最后，本文从社会网络关系的角度分析了会计师事务所内部审计师之间的传染效应。结果显示，虽然整体而言分所内其他审计师没有受到低质量审计师的影响，其中与低质量审计师曾经共事过或者存在校友关系的审计师审计质量显著低于其他人，说明共事以及校友关系会导致分所内审计师之间传染效应的发生。

Enron which was the seventh largest firm in revenues in the United States went to bankruptcy in 2001. Due to the audit failure in the Enron Company, Anderson’s reputation was damaged severely and barred from conducting and reporting on the audits as the fifth largest auditing firm in the world. During the days following disclosure of Anderson’s audit failure evidence, Anderson’s other clients experienced a statistically negative market reaction, suggesting that investors downgraded the quality of the audits performed by Anderson. The question that how stakeholders evaluate audit quality more accurately becomes the critical issue which is concerned by both the academics and regulators. Extant studies provide the evidence of contagion effect of restatements at the audit firm level or audit office level, which means that the presence of restatements in an engagement office indicates the low quality audits of other audit clients. Based on the unique data about public individual auditor information in China, this paper focuses on the contagion effect of restatements and the associated economic consequences at the level of individual audit partners, and how the social networks between individual audit partners affect the contagion effect of restatements among individual audit partners within the same audit office. We state our empirical evidence from three perspectives in the following:Firstly, in general, we find the empirical results that are consistent with the existence of contagion effect of restatements at the level of individual audit partners. We find that the quality of audited earnings is much lower for clients in the individual-years with the misstatement occurred, compared with a control sample of individual-years without misstatements. Further evidence shows that the contagion effect of restatements at the level of individual audit partners exists only in the Non-Top 10 audit firms, only in the Non-Partnership audit firms and only in the clients with individual-years where the individual audit partners are busier. Finally, we also find the evidence about different contagion effects of different types of restatements. Secondly, our empirical results show that the individual auditors experience a loss in audit market share following client restatements, in terms of client number loss, client size loss and audit fee loss. Further analysis indicates that client restatement announcement impair the associated individuals’ ability to both attract and retain audit clients. Evidence from the client-year data shows that the likelihood of individual audit partner change is much higher for the clients with individual auditors associated with restatements. And for the clients that do not change the individual audit partners, the likelihood of audit fee decline is much higher for the clients with individual audit partners associated with restatements. In the capital market, we also find that the investors can see through the low quality of individual audit partners, since the earnings response coefficients are reduced when restatements are publicly announced for the clients audited by the individual audit partners associated with restatements, but it will not last after the restatement year. Finally, we investigate the effect of social network on the contagion effect among the individual audit partners within the same audit office. In general, there is no contagion effect of restatements among the individual auditors within the same audit office. But we find that when there are some work ties or school ties between individual auditor without client restatements and low quality individual auditor with client restatements in the same audit office, the former individual audits’ clients suffer a lower audit quality. The empirical results indicate that there exist contagion effect of restatements among the individual auditors within the audit offices when they have some social connection.