中文摘要：

本文基于世界银行2003年和2005年的调查数据，对不同所有制企业的契约实施环境进行了比较。研究发现，民营企业的契约实施环境显著差于其他所有制类型的企业。在此基础上，我们进一步考察了政治关联对企业契约实施环境的影响。实证结果表明：（1）与掌握实权的政府官员建立政治联系能够改善民营企业的契约实施环境，而且这些官员的地位越高，其影响越显著；（2）政治关联是否能够改善企业的契约实施环境与官员的类型有关，如果官员属于“帮助企业发展”类型的，则与此类官员的政治关联能够改善企业在本省和外省的契约实施环境；（3）董事会中有政府官员以及总经理是由政府任命不利于企业契约的实施环境的改善；（4）随着法律制度的不断完善和市场化进程的推进，各类政治关联对企业契约实施环境的积极作用正在被其消极作用所抵消。因此，消除阻碍民营企业发展的各种制度和政策障碍仍然是推动民营企业发展的根本之道。

英文摘要：

Based on the survey data of World Bank＇s 2003 and 2005 on Chinese firms, this paper investigates the contract enforcement environments for business in China. It shows that the contract enforcement environment of private firms is significantly worse than that of non-private firms. Using endogenous switching model and propensity score matching method, we investigate how political connections affect firms＇ contract enforcement environments. It is found that political connections with ＂competent officials＂ significantly improve firms＇ con- tract enforcement environments, especially for private firms. The effect also depends on the ＂types＂ of the officials. Nevertheless, whether there are government officials in board, or the general manager is appointed by government, does not significantly affect a firm＇s contract en- forcement environment. Finally, political connections are more helpful in 2003 than in 2005.