study their export participation and entry decisions.<sup>10</sup> Finally, we use two alternative measures to proxy for the regulation intensity at the product level. First, we use the WTO Specific Trade Concerns (STC) Database, which provides product-level (HS4) information on trade concerns raised in the WTO’s SPS and TBT committees. The main advantage of this database is that it captures the “revealed” stringency of standards, as perceived as important trade barriers by exporters, rather than counting the number of standards that may or may not be trade impeding (Fontagné et al., 2015; Fontagné and Orefice, 2018). We classify products to be regulation intensive if at least a concern was raised to one of the committees. There are 312 specific concerns raised on 124 products in the SPS committee and 317 specific concerns raised on 848 products in the TBT committee, together covering a broad range of 863 products across different industries (see Appendix Table A.4 for the distribution of STC-products across industries). Second, we use an alternative measure of regulation intensity based on prior notice requirements by the United States’ Food and Drug Administration (FDA). This measure covers a total of 272 HS4-products, mainly in food, drugs, and medical devices, which require prior notice to the FDA.<sup>11</sup> To construct the data set needed for the first part of our analysis (firm-level), we expand the initial exporters database to make it squared so that every firm-destinationyear combination is an observation. For the second part of our analysis using the product-level data, we first aggregate firms’ exports data (available at HS6-level) to the HS4-level, which is the level available in the WTO STC data set. Then, we expand the data set so that each firm-product that exported at least once is combined with every destination and year. There are 12,918 firms exporting 1,197 HS4-products to 115 destinations, and there are 102,295 firm-product combinations that are exported at least once.<sup>12</sup> This expanded panel data set allows us to include a rich set of fixed effects and exploit firms’ previous export experience to estimate the effect of RTAs on non-member country firms.

Using this data set, we construct two dependent variables: firm export participation and entry dummies. The export participation dummy is equal to 1 if firm _i_ exports to destination _j_ in year _t_ , and equal to 0 otherwise. The export entry dummy is equal to

> 10On average, 27% of exporting firms each year are new entrants. Appendix Table A.3 provides yearly statistics on exporting firms and the share of new entrants.

> 11The distribution across industries of products subject to FDA prior notice is reported in Appendix Table A.5. Products are listed at the HS10-level which we aggregate up to HS4-level to be consistent with the level of disaggregation in the WTO STC data set. The list of products that require prior notice to the FDA were downloaded, in June 2018, from https://wayback.archive-it.org/7993/20170721215512/https://www.fda.gov/Food/ GuidanceRegulation/GuidanceDocumentsRegulatoryInformation/ImportsExports/ucm170031.htm.

> 12This means that we have 12 _,_ 918 _×_ 115 _×_ 15 = 22 _,_ 283 _,_ 550 observations in the expanded firm-level data set and 102 _,_ 295 _×_ 115 _×_ 15 = 176 _,_ 458 _,_ 875 observations in the expanded firm-product-level data set. Note that the vast majority of these observations are filled with zero trade flows, but are needed for the

5