Before revision:  A reassessment of the most commonly studied determinants of the extensive margin of trade demonstrates that both true state dependence and unobserved heterogeneity contribute strongly to trade persistence and that taking this persistence into account matters significantly in identifying the effects of trade policies on the extensive margin.
After revision:  A reassessment of the most commonly studied determinants of the extensive margin of trade demonstrates that both true state dependence and unobserved heterogeneity contribute considerably to trade persistence and that taking this persistence into account matters significantly in identifying the effects of trade policies on the extensive margin.