and countries. Firms' export decisions depend on a combination of firm “productivity” and firm-product-country “consumer … tastes,' both of which are stochastic and unknown prior to the payment of a sunk cost of entry. Higher-productivity firms … export a wider range of products to a larger set of countries than lower-productivity firms. Trade liberalization induces …

relationship between the margins of trade and firm productivity, both across firms and within firms over time. In addition, we … and the value of CAT exports responds differently to variation in firm productivity and trade costs than does the export …