We control for additional country characteristics. We use the Ease of Doing Business index (EDBc) and the Trading Across Borders index (TABc) to control for the quality of the business environment in the exporting country. A country’s ranking on the former is based on the average of ten subindices–including starting a business, dealing with licenses, hiring and ...ring workers. More speci...cally, the Trading Across Borders index, captures the complexity of customs procedures faced by exporters. It accounts for the number of documents, the number of signatures and time necessary to export and import. The data for both indices is taken from the WBDBS. We use the Logistics Performance Index as a proxy for exporting country’s capacity to e¢ ciently move goods and connect with international markets (LPIc). The index is a weighted average of country scores on six key dimensions–including e¢ ciency of the clearance process, competence and quality of logistics services, ease of arranging competitively priced shipments. Additionally, we control for the quality of trade and transport infrastructures using the Infrastructure Index which enters the overall LPI index. The data comes from the World Bank Logistic Performance Indicator database for the year 2007<sup>16</sup> .

Product wise, we use a perishability index, to insure that our risk measure is not picking up on other product characteristics that may a¤ect their survival. The index takes value one if the product cannot be stored without refrigerator facilities, zero otherwise. Perishable products typically include, meat, ...shery products, fruits and vegetables. Correlation between our risk index and the perishability index is 0:15. Finally, data for the gravity variables come from the CEPII database.

# 4.3 Descriptive Statistics

Appendix 8:F reports some statistics at the ...rm level for each exporting country. "Risky" products account for an important share of ...rms total exports in all ...ve countries. Additionally, "risky" ...rms–exporting at least one "risky" product–represent around half of the total ...rm population in all ...ve countries. Non "risky" ...rms are ...rms that export no "risky" products at all. Appendices 8:G and 8:H report some statistics for our survival data. Considering ...rms in all countries the average spell duration is about one year and four months and the median duration is only one year. Almost 40% of the spells are right censored, and 17% are left censored. Considering each country individually, Senegal exhibits the highest average spell duration, and Ghana the lowest. A large proportion of spells, 56%, start with trade values lower than 10’000 dollars, 13% are initiated with trade values higher than 100’000 dollars and only 3% start with initial trade values greater than 1’000’000 dollars. Dropping all spells with initial trade value inferior to 10’000 dollars (100’000, or 1’000’000 dollars) increase (even more) the average and median spell duration. The higher the initial trade value the higher the probability to survive. These results are in line with ...ndings in previous empirical studies (Besedes and Prusa, 2006a, 2006b).

We now move on to characterize the duration of trade relationships non paramet14