border barrier was dismantled.<sup>105</sup> Second, we have attempted in our analysis to refrain from passing judgment on any particular BTB policy; i.e., our selection of BTB policies should not be construed as a commentary on their trade restrictiveness or on any particular WTO legal decision. Indeed, a close read of more than 20 years and 100 WTO legal decisions indicates a surefire tension that has arisen but which also speaks again to the complexities involved in research in this area. On one hand, the WTO’s Dispute Settlement Body (DSB) almost never questions the legitimacy of the respondent country’s underlying domestic policy under dispute; i.e., the WTO approach seems to respect national sovereignty and its member governments’ right to regulate to address market failures and externalities. On the other hand, in almost every dispute, the DSB also finds that the respondent country has done something fundamentally wrong via the manner though which it has _applied_ its BTB policy.

# **6 Conclusion**

We have presented a portrait of the complexity of international commercial policy as of 2013-2014 and have provided answers to some of our chapter’s fundamental questions regarding variation in the levels of import protection in place today - across countries, within countries across sectors, over time, and vis-`a-vis different trading partners in a discriminatory manner. However, most of our main questions remain only partially answered. The inability of the current literature to completely assess these questions - especially with respect to the overall restrictiveness of policy, but also with respect to the trade restrictiveness of the ‘newest’ policies of interest that are behind-the-border - provides an opportunity. Indeed, with increasing access to policy data, a long-term research agenda directed toward an improved understanding of trade policy is not only likely to bear fruit scientifically, but it is also likely to result in large societal payoffs. Before concluding, we take the opportunity to suggest additional ways through which these newly available policy data sources may improve our understanding of other areas of the international economy.

Over the last decade, empirical research on firms engaged in international trade has exploded. This includes firms involved in multi-country production through foreign direct investment, and in cross-border production structures and global supply chains. Scholars have provided a sound understanding of many of the differences between manufacturing firms that operate domestically and those that engage globally.

However, while these firm-level studies are informed by a wealth of data on the destinations for their outputs, origin of inputs, prices, quantities, worker matching, revenues, debts, firm-to-firm relations, etc. - they most often treat the policy environment as an afterthought. The richness of changes in the trade policy barriers, which we have documented result in considerable heterogeneity

> 105Another limitation of our approach is that it does not attempt to provide even a cross-section of imposed BTB policies in existence at any moment in time - i.e., some of the BTB policies highlighted here may no longer be in effect. See also the survey and compilation of policies provided in WTO (2012).

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