中文摘要：

已有研究表明风险投资机构的网络位置对成功退出有重要影响，但影响机理尚未揭示。本文以Heek-man模型为基础构建一个两步回归模型研究风险投资机构网络位置影响成功退出的机理。先通过第一步选择模型计算出反米尔斯比率，然后在第二步回归模型中引入反米尔斯比率，从网络位置对成功退出的总影响作用中分离出项目选择和增值服务各自的影响作用。运用清科数据库2000年1月1日至2009年12月31日的数据，本文研究发现：在联合投资网络中处于有利位置的风险投资机构既可以选择到高质量的风险项目，也可以为风险项目提供高质量的增值服务，因而能够实现更高的成功退出率。

英文摘要：

Researches have shown that venture capital firms＇ network position has a significant influence on their successful exit, however the mechanism of this influence has not yet been revealed. On the basis of Heckman model, a two - step model is constructed to study this influence. In the first place, the inverse Mills ratio is calculated by the first - step selection model, and then the inverse Mills ratio is introduced into the second - step regression model in order to separate the effect of venture selection and value - added services, respectively from the overall influences of venture capital firms＇ network position on their successful exit. With the data of Zero2IPO Database from January 1, 2000 to December 31, 2009, it is found that venture capital finns standing on a vantage point in co - investment network not only could select high - quality ventures, but also could provide high - quality value - added services to them, therefore they are able to achieve a higher ratio of successful exit.