For pork, which is a marginally exported commodity subject to import tariffs, the price gap has been set to zero. The average import unit value at the Vietnamese border is used for maize. For the remaining four commodities, a variety of alternative reference prices are used because of the limited volume of imports into Viet Nam: the average Thailand FOB price for refined sugar, the average Australian FOB price for beef and veal, the average Chinese FOB price for poultry and the Chinese farm gate price for eggs. For all but one product, coffee, margins were calculated as a fixed percentage of the farm gate price based on discussion with MARD.