中文摘要：

如何科学合理地测算贸易产品质量是研究企业产品质量异质性的一个关键问题,但目前仍缺乏一个被广泛认可的方法,也没有相关研究对不同方法的结果进行比较和检验。文章基于国家层面的进口质量、企业层面的出口质量和企业层面的进口质量三个视角,将已有研究方法进行归类,并利用中国数据进行测算和检验,力求找到不同视角下最符合中国现实的测算方法。研究表明：（1）国家层面的进口质量测算使用KHW方法,而企业层面的出口质量测算则使用SHIBZ方法更加符合中国现实;（2）对于企业层面的进口质量测算,通过引入运输成本和汇率作为产品价格的工具变量对现有方法加以改进,可以克服其存在的样本选择偏差等问题;（3）对贸易产品质量测算方法在国家层面与企业层面、进口方面和出口方面进行划分,其测算结果能够合理地解释我国近年来的进出口产品质量变动趋势,且国家层面与企业层面的一般贸易进口产品质量的变动趋势一致。文章不仅为今后研究中国进出口产品质量问题提供了测算依据,而且有助于我们廓清我国进出口产品质量的现实情况及其变动趋势。

英文摘要：

How to measure trade product quality scientifically and reasonably is a key problem to study the heterogeneity of enterprise product quality.But it still lacks a widely recognized method.And there is no related research to compare and test the results of different methods.From the perspectives of import quality at national level,export quality at firm level and import quality at firm level,this paper puts the main measuring methods into three categories,and measures tests the Chinese data to find out the most suitable measurement method as for Chinese fact from different perspectives.It arrives at the results as follows：firstly,the application of KHW and SHIBZ into the measurement of import quality at national level and export quality at firm level respectively is more suitable for Chinese fact;secondly,as for the measurement of import quality at firm level,the improvement of current methods by the introduction of transportation costs and exchange rates as instrumental variables of product prices can be used to overcome the problems like sample selection bias;thirdly,the measurement results after the classification of measurement methods of trade product quality at national and firm levels and in import and export aspects can provide a reasonable explanation for changing trends of Chinese import and export product quality in recent years,and the changing trend of general trade import product quality at national level is consistent with the one at firm level.It not only provides measurement reference for future study of Chinese import and export product quality,but also helps us to clarify the reality of import and export product quality and change trend in China.