中文摘要：

公司财务决策的同群效应是最近国际财务学界开始关注的新问题，而具体到并购决策同群效应的研究仍属鲜见。本文以2003-2014年A股上市公司并购事件为例，研究了公司并购决策中的行业同群效应及其形成机制。实证研究发现，上市公司的并购决策存在明显的行业同群效应，即上市公司在做出并购决策时会明显受到同行业其他公司并购行为的影响；结合模仿定律的研究发现，同群效应服从逻辑模仿律，同群者并购绩效越好时同群效应越明显，并且服从先内后外律，具有相同产权性质的公司之间的同群效应更为明显；形成机制研究表明，信息获取性模仿和竞争性模仿是促使同群效应形成的重要内在机制；最后还发现，公司规模及公司治理对行业同群效应存在重要影响。本文研究将在较大程度上丰富国际范围内的公司并购和同群效应研究成果。

英文摘要：

Peer Effect is a theoretical concept of social psychology, which suggests that an actor＇s behavior will be influenced by its peers. The peer effect in financial decisions is a new topic concerned by scholars of finance, and the literature about peer effect in M＆A decision is rare. Using the sample of A-share listed companies from 2003 to 2014, this article investigates into the industry peer effect in M＆A decisions and its formation mechanism. The results show that the industry peer effect in M＆A decisions of China＇s listed companies is really exist, which means that the M＆A decision of a firm will be affected by its industry peers. This paper also discloses that peer effects comply with the logic law of imitation with the evidence that peer effect is more obvious when M＆A performance of peers is better, and it also complies with the closer-preference law of imitation with the evidence that peer effect of those having the same property rights characters is more obvious. Furthermore, this paper investigates the formation mechanisms of peer effects on M＆A decision. The results show that the firms＇ experience of M＆A has negative interactive influence on peer effects, which suggests information-based imitation is an underlying formation mechanism. The results also show that the level of industrial competition has positive interactive influence on peer effects, which suggests rivalry-based imitation is another underlying formation mechanism. It also shows that firm sizes and qualities of corporate governance have significant influence on peer effects. Bigger firms and firms with higher corporate governance qualities have more influence on their industry peers. Compared to existing literature, this paper provides a new theoretical perspective on M＆A decision, and it also provides further empirical evidence of peer effects in corporate business decisions. In a word, this paper will enrich the M＆A research and peer effects research, and give some enlightenment to practitioners.