that they are no longer primarily about tari¤ liberalization but instead are pushing toward deeper integration that addresses non-tari¤ and behind-the-border policies.<sup>16</sup> The nascent literature on deeper integration currently splits new PTA issue areas into two categories. The ...rst are “WTOplus” PTA provisions - i.e., those that also exist under the WTO, but where PTA members use their agreement to take on commitments to go further. Tari¤s are the clearest example; e.g., WTO members make legally binding MFN tari¤ commitments, and PTAs involve partners lowering at least some of those tari¤s toward each other even further. Other examples include services, intellectual property rights, and product standards - each of which has at least some basic WTO coverage. The second category for PTA provisions are “WTO-extra”areas, and these involve issues that are not yet explicitly addressed by the WTO. Examples of WTO-extra areas include labor standards, environmental standards, foreign direct investment provisions, movement of capital, competition policy, data protection, and even potential cooperation over other domestic regulations in order to help achieve improved levels of “regulatory coherence”across PTA member countries.

Horn, Mavroidis, and Sapir (2010) characterize the “depth”of PTA provisions by applying this categorization to the many US and EU PTAs in existence as of 2008.<sup>17</sup> The initial evidence was that EU PTAs tend to have many more WTO-extra provisions but that the pattern is reversed when the analysis conditions on the legal enforceability (under dispute settlement) of the provisions, as US PTAs contain more legally enforceable WTO-extra provisions. In follow-up work, the WTO (2011, Section D) extended this approach in order to characterize 14 di¤erent “WTO-plus”provisions and 38 di¤erent “WTO-extra” provisions for a wider sample of PTAs, including a number involving only developing countries. Their work has established a new and rich set of databases for future research to explore the heterogeneity in application of these provisions across di¤erent PTAs.

Dispute settlement under PTAs In contrast to the WTO, there is very little empirical record of sustained and e¤ective dispute resolution taking place under the major PTAs. With the exception of the EU, dispute settlement provisions in most PTAs have rarely been used, and when actually triggered, their record of resolving disputes is mixed at best.<sup>18</sup> It is also not uncommon for the use 16 Some of these non-tari¤ policies under negotiation are applied at the border. For example, policies like antidumping and safeguards are applied at the border but frequently as quotas or price undertakings. Other examples of non-tari¤ barriers that arise at the border may include customs regulations, import valuation, etc. 17 Other recent contributions characterizing and assessing such PTA provisions include work by WTO Secretariat legal sta¤ (Chase et al, 2013) and political scientists (Elsig and Allee, 2015). Note that the latter assess a larger coverage of dispute settlement provisions in preferential agreements in a publicly available “design of trade agreements’‘ (DESTA) database (Dür, Baccini, and Elsig, 2014). See also WTO (2011).

> 18 The EU has a di¤erent institutional design, including a supra-national framework that initiates disputes against member states from within and thus does not rely exclusively on the “state-to-state”framework of dispute resolution found in the WTO and many other PTAs. One result is that the EU’s dispute settlement provisions have led to thousands of disputes. Tallberg and Smith (2014, p. 126) report that the supranational European Commission initiated more than 30,000 cases over 1978-2009 against its member states. Furthermore, the Commission only referred 11.5 percent of these initiated disputes to the European Court of Justice for a legal decision. On the other hand, EU member states have initiated only a handful of disputes against one another. Finally, the EU’s free trade agreement with Iceland, Liechtenstein, and Norway under EFTA contains a supranational Surveillance Authority (SA) modeled similarly to the European Commission; Tallberg and Smith (2014, p. 138) report that the SA initiated roughly 400 disputes against the three EFTA member states over 1994-2008 and that the member states ...led zero EFTA disputes against one another during this period.

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