For governments, the advantage of non-tariff barriers (NTBs) to trade is that their effects are more certain than for tariffs. Now that tariff barriers have been substantially reduced, there has been increasing interest in the ways that non-tariff barriers (NTBs) may distort and restrict international trade. This working paper assesses currently available methods for quantifying NTBs. Calculation of the tariff equivalent of a given NTB for a given economic indicator is complex, and requires a great deal of information. Measures that are equivalent for one indicator will not be so for others, and there is no substitute for NTB-specific expertise ...