AER论文+数据+dofile  市场竞争+价格加成（markup）与贸易应盈余
markup  是 ds框架下  ces生产函数推导出的 价格加成
并不是售价高出 成本 价格的部分，

We study the procompetitive gains from international trade in a
quantitative model with endogenously variable markups. We find that
trade can significantly reduce markup distortions if two conditions
are satisfied: (i) there is extensive misallocation, and (ii) opening
to trade exposes hitherto dominant producers to greater competi
tive pressure. We measure the extent to which these two conditions
are satisfied in Taiwanese producer-level data. Versions of our model
consistent with the Taiwanese data predict that opening up to trade
strongly increases competition and reduces markup distortions by
up to one-half, thus significantly reducing productivity losses due to
misallocation.