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Abstract
This study estimates the effect of a diverse group of 30 PTAs on members’ trade of 26 agri-food
products categorized into eight commodity sectors for 1990, 1995, 2000 and 2000 using
disaggregated trade data for 40 countries and the Heckman selection model. Results show that
whether reported zero trade-flows are considered actual or potential affects the size of the
estimated PTA impacts. However, irrespective of the true nature of the zero trade-flows, the
effects of PTAs are found positive and statistically significant. OLS estimates fall between the
Heckman-model-derived conditional and unconditional effects of PTAs.