中文摘要：

保持出口贸易持续平稳发展对提升企业生产率进而培育外贸竞争新优势，具有重要战略意义。利用1998～2007年中国工业企业数据，通过Kaplan—Meier方法估计证实了出口具有显著的负向时间依赖特征，且贸易关系存在异质性．即资本技术密集型、高出口密集度和高生产率的企业具有更长的出口持续时间。此后利用多种实证方案也发现：出口持续时间的延长显著提升了企业生产率水平，即存在出口学习效应；且资本技术密集型、低出口密集度的企业通过持续出口获取的生产率提升更为显著，劳动力密集型、高出口密集度企业则相对较小。基于生产率动态分解的分析也表明，我国出口企业的生产率优势很大程度上来源于竞争引致的优胜劣汰。因此．稳定贸易联系、延长企业出口持续时间是新常态下推动贸易发展方式转变的重要路径。

英文摘要：

It is strategically important to improve firms＇ productivity and foster new competitive advantages through maintaining trade relationship. Based on the China＇s industrial enterprises＇ data （CIED） in 1998-2007, this paper uses Kaplan-Meier method estimating China＇s firms＇ export duration. Results show that it has significant negative duration dependence for China＇s export firms and the capital and technology intensive firms, high export intensity firms and high productivity firms have longer export duration. Then many empirical methods prove that export duration significantly enhances firms＇ productivity and the positive effect is more significant with capital and technology intensive firms, low export intensity firms and the effect for labor intensive firms and high export intensity firms is relative smaller. Further, based on the dynamic decomposition of productivity, we find the productivity advantages of China＇s export firms are mainly from the survival of the fittest in market competition. Therefore, maintaining trade relations and extending export duration are important for changing trade mode under China＇s new normal.