中文摘要：

基于国有企业改制的样本，本文利用双重差分法发现。在相同条件下，国有企业长期投资水平低于非国有企业．这可能是造成国有企业投资非效率的重要因素。而这一点却是既有文献所忽视的。本文从委托一代理的理论视角出发，剖析国有企业董事长的约束机制和激励机制．以期揭示国有企业长期投资偏低的深层原因。文中利用国有企业董事长总任期刻画其约束机制．利用国有企业董事长的持股数占总股本的比例来测度其激励机制。OLS回归结果显示，国有企业董事长总任期越短，长期投资越少，而持股比例对长期投资无显著影响：非国有企业董事长总任期对长期投资无显著影响，而持股比例越高，长期投资越少。为克服OLS回归中的内生性问题．论文进一步利用IV估计验证了以上结论。这意味着．引入股权激励这类市场化的激励机制并不能有效改善国有企业长期投资不足的问题，而只有放松国有企业委托一代理机制所带来的约束．至少是对董事长等战略决策者的行为约束，才是解决国有企业长期投资不足、继而改善其投资非效率的有效途径。

英文摘要：

Using a quasi-natural experiment method and CSMAR data, we find out that the effect of state- owned enterprises （SOEs） reform on the long run investment is positive. This may be one of the factors that cause the low efficiency of SOEs which has been ignored in the previous research. We try to explain this phenomenon from the angles of constrain and incentive on the board chairmen in SOEs. We use the term of board chairmen in SOEs as the proxy variable of constrain, and the stock option incentive of the board chairmen in SOEs as the proxy of incentive. The OLS regressions show that, the shorter the term of board chairmen in SOE, the less the long run investment is, while the stock option incentive has no impact on it. In order to dealing with the endogenous problem, we find an instrument variable for the term of the board chairman. The IV results confirmed what we have found. Those imply, the reason of the low level of long run investment in SOEs is the over- constrained on the board chairmen, not the lack of incentive. The effective way to increase the long run investment in SOEs is to relax the constrain on the board chairman.