Cumulation and ITC Decision-Making: The Sum of the Parts is Greater Than the Whole

In 1984 Congress amended the antidumping and countervailing duty laws, mandating that the ITC ``cumulate'' imports across countries when determining injury. We estimate that cumulation increases the probability of an affirmative injury determination by 20 to 30 percent and has changed the ITC's decision (from negative to affirmative) for about one-third of cumulated cases. We also show that the protective effect of cumulation increases as the number of countries involved increases, holding import market share constant. That is, cumulated imports have a super-additive effect on ITC decision-making.