Western countries worry about the dramatic price reduction and talk about dumping.

西方国家担心价格骤跌，谈论倾销。

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Some of those comparisons produce positive dumping margins (whenever the U.S. price is lower than the home market price) and some yield negative dumping margins (whenever the U.S. price is higher than the home market price).

FORBES: Protectionist Antidumping Regime is a Pox on America's Glass House

For each comparison, the difference between the U.S. price and the home market price is considered the unit margin of dumping.

FORBES: Protectionist Antidumping Regime is a Pox on America's Glass House

The justification for the exception under Article 2.4.2 is, presumably, that that comparison methodology allows the authorities to home in on targeted dumping, which may be revealed by patterns of price differences among purchasers, regions or time periods.

FORBES: Protectionist Antidumping Regime is a Pox on America's Glass House