A Portrait of Trade in Value-Added over Four Decades
利用1970-2009年贸易、生产和投入数据，发现全球增加值与总出口比率下降约10个百分点，制造业降幅达20个百分点，而贸易摩擦变化是主因。
We combine data on trade, production, and input use to document changes in the value added content of trade between 1970 and 2009. The ratio of value-added to gross exports fell by roughly 10 percentage points worldwide. The ratio declined 20 percentage points in manufacturing, but rose in non-manufacturing sectors. Declines also differ across countries and trade partners: they are larger for fast growing countries, for nearby trade partners, and among partners that adopt regional trade agreements. Using a multi-sector structural gravity model with input-output linkages, we show that changes in trade frictions play a dominant role in explaining all these facts.