values and volumes and relatively larger potential declines in exporter-received prices than do respondent policies that apply to a selective set of exporters.

One contributing explanation may be that disputes involving antidumping in particular are different, and this is driving the results of the partial policy sample.<sup>26</sup> The substantial research literature on antidumping reveals that it has a number of peculiar features as an import-restricting policy. For example, in the United States it may be counterproductive for the (complainant) exporter to attempt to retain market share and stabilize the volume of its exports by further lowering its prices in response to the import restriction. Because the size of the antidumping duty is calculated retrospectively, a further reduction of its export price may simply result in the antidumping authority increasing the size of the calculated dumping margin and thus the size of the import duty that it imposes.<sup>27</sup> On the other hand, it is also important to point out that these particular differences may be spurious and arise due to standard problems of using unit values at the HS-06 level, which can be a relatively noisy measures of prices. For example, the HS-06 level is still relatively aggregated in that it is may be comprised of many underlying varieties of HS-08 or HS-10 varieties with different uses, made of different qualities and by heterogeneous firms with differential markups. As an extreme example to illustrate the point, suppose a respondent’s policy targets only the lowest-priced HS-08 variety and completely eliminates all imports of that variety. The result may be that unit values at the HS-06 level increase even though the HS-06 level price increase does not reveal any useful information about the price change happening at the underlying HS-08 level by definition. An open research question is whether there are any greater measurement problems involved in using HS-06 data for partial policy disputes, relative to global policy disputes.

We conclude this section by considering why potential differentials may be useful for empirical research on determinants of WTO dispute settlement activity. Consider, for example, a study like Bown (2005b), that explores the question of which of the exporters hit by previously-imposed antidumping duties will ultimately challenge those duties under formal WTO dispute settlement, or a modified version of Bown (2005a), that would examine the set of all previously-imposed and MFN-conforming global

> 26 Disputes over antidumping account for 62 percent of our subsample of partial policies, and a large share of these antidumping disputes challenge US-imposed antidumping. While not reported in the table, a comparison between antidumping and other partial policy disputes indicates that antidumping violations are associated with even larger decreases in trade volumes (46.2 percent compared to 34.1 percent on average) and increases in unit prices (1.9 percent increase compared to a 0.9 percent decrease on average), although these differences are not statistically significant.

> 27 Blonigen and Haynes (2002, 2010), for example, provide a discussion and empirical analysis of US antidumping duties and implications for export prices based on an Canadian steel exports. See also Kelly (2010).

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