本课题致力于完善现有贸易成本测算体系，构建多维贸易成本统一框架。在考虑交通运输路径、贸易运输时间、贸易不确定性及企业位置等因素的前提下，测算了国家间宏观贸易成本，以及产品和企业层面的微观贸易成本，并将其纳入了多维贸易成本的统一框架。首次在超越对数框架下，纳入全球价值链和多维贸易成本，来分析贸易成本变化所带来的贸易流量和贸易福利效应，创新性地提出了GVC视角下的第三国效应，并对贸易福利进行事前估计和反事实估计，发现贸易福利变动的新来源。此外，首次基于非位似偏好的视角，考察异质性需求偏好下区域集团层面（区域内）贸易成本变化对本地市场效应的存在条件和作用机制，突破现有研究中仅考察同位似偏好下国家或行业层面本地市场效应的相关验证。基于新测度的指标和理论结论，本课题进行了一系列的实证工作，并对“一带一路”中基础设施建设项目，贸易协定等的贸易流量效应、贸易福利效应和区域本地市场效应进行综合评估。

This project is committed to promote and improve the existing trade cost measurement system, and build a multi-dimensional unified framework of trade costs. On the premise of considering transportation path, trade transportation time, trade uncertainty, enterprise location and other factors, this project calculates the macro trade costs between countries, as well as the micro trade costs at the level of products and enterprises, and then it integrates them into the unified framework of multi-dimensional trade costs. For the first time, this project introduces the global value chain and multi-dimensional trade costs into the logarithmic framework to analyze the trade flows effect and trade welfare effect brought by the changes of trade costs. In this model, this project proposes the third country effect from the perspective of GVC innovatively, and makes prior estimation and counterfactual estimation of trade welfare to discover new sources of trade welfare. In addition, based on the perspective of non-homothetic preference for the first time, this project studies the existence conditions and mechanism of home market effect of the change of trade cost at the regional group level under the heterogeneous demand preference, which breaks through the relevant verification of the home market effect under homothetic preference for the country or industry level..Based on the new index and theoretical conclusions, the project carries out a series of empirical work, and evaluates comprehensively the trade flow effect, trade welfare effect and regional home market effect of infrastructure construction projects in "the Belt and Road" and trade agreements.