Appropriate assessment of the social value of market access is at the core of a broad range of inquiries in trade research. A selection include: the appraisal of industry-level production and consumption distortions due to selective trade liberalization and partial tax reform; the construction of national-level quantity indicators of market access consistent with welfare change, and the use of international trade re-balancing as sanctions to discourage trade agreement violations, or as compensation in trade dispute settlement. In order to obtain shadow prices, we propose a new approach integrating the Luenberger benet function and the directional output distance function. This yields a trade benet function which represents trade preferences a la Meade in the context of a canonical general equilibrium model of trade. We rst show that our approach is in keeping with well-established and commonly used measurement techniques of trade welfare, for the standard trade expenditure function is in fact dual to the trade benet function. We then show that this dual relation allows for a direct retrieval of the shadow values of net imports from the trade benet function. The usefulness and operationality of our approach is then demonstrated in a series of applications and simulations.