the set of products that countries have committed to legally bind, there can be signi...cant di¤erentials between applied rates and the binding commitment. This last point holds for all of the G20 emerging economies (including Argentina, Brazil, India, and Mexico) with the exception of the relatively new WTO accession countries of China (2001) and Russia (2012), for which the existing membership demands included relatively low levels of MFN tari¤ bindings.<sup>7</sup> Heterogeneity across the tari¤ data can be even more extreme for other major (but poorer) developing countries. Some WTO members (e.g., Bangladesh, Burma, Nigeria) have committed to upper limits for tari¤ bindings on fewer than 20 percent of their import tari¤ lines. Even on products for which these WTO members bind their tari¤s, the average binding rates may be more than 100 percentage points higher than applied rates.

There are also important di¤erences in applied MFN tari¤ heterogeneity within countries across sectors. As one important example, Table 3 shows many instances of sharp di¤erences between average applied tari¤s in agricultural products relative to overall rates of protection. Within the G20, a few countries such as Argentina, Australia, and Brazil o¤er lower average import tari¤s for agriculture than they do for other products. For most others, however, the rates in agriculture are substantially higher (Anderson, Rausser, and Swinnen, 2013).

Finally, applied MFN tari¤s are not the only important trade policy instrument within the multilateral WTO system. An increasing number of countries since the early 1990s have begun to invoke GATT/WTO exceptions to their negotiated tari¤ bindings and use the temporary trade barrier (TTB) policies of antidumping, safeguards, and countervailing duties.

Before 1990, industrialized economies such as Australia, Canada, the EU and the US dominated overall use of TTBs, and especially the most predominant antidumping policy (Blonigen and Prusa, 2003). Since the early 1990s, a number of emerging economies have subsequently become major users of TTBs (Bown, 2011a) as they reduced their applied import tari¤s. The last column of Table 3 provides data on the import coverage of the TTBs cumulatively applied in 2012. As examples, eleven di¤erent G20 economies had more than 1 percent of their tari¤ lines also subject to an imposed TTB in 2012; some of these countries did not even have an antidumping law in place 25 years earlier. Many also had one or more episodes over this 25 year period during which the cumulative TTB import coverage rose to as high as 4-6 percent.

Table 3 reveals two other features of TTB use. First, not all WTO members use these policies. Indeed most of the poorest WTO members have never implemented a formal antidumping or safeguard proceeding, a feature that can be partially explained by the fact that the tari¤ bindings of these countries are su¢ ciently above their applied rates that they can adjust tari¤s upward unilaterally in response to shocks. Second, even members of a customs union –i.e., countries that eliminate tari¤s on internal trade with each other and share a common applied MFN tari¤ toward non-members, examples of which we describe in more detail below – do not necessarily apply a common set of TTB policies. In 2012, for example, customs union partners Argentina and Brazil

> 7 As of 2012, Russia had not yet fully phased in its MFN applied tari¤ cuts under its WTO accession terms and thus its average applied rate was still above its average binding commitment.

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