Schemes for aggregating preferential tariffs in agriculture, export volume effects, and African LDCs.

摘要

Import-weighted aggregated tariffs are often used in analyzing issues of erosion of non-reciprocal preferences. This paper argues that commonly used import-weighted tariffs under-estimate the true level of protection on imports originated from preference-receiving countries, especially the African least developed countries (LDC)s (ALDCs). The theoretical discussion of this paper suggests that when used in numerical simulations of preference erosion and expansion scenarios, import-weighted tariffs tend to incorrectly downplay the preference erosion effect of most favoured nation's tariff cuts, and understate the export promotion effect of expanding preferences. As an alternative to the import-weight method, a simple average method is used to calculate aggregated tariffs imposed on ALDCs. These are shown to be indeed higher than their import-weighted counterparts aggregated from the same disaggregated source. Numerical simulations conducted with the two sets of aggregated tariffs confirm the theoretical discussion and suggest that the issues of preference erosion and preference expansion should be taken more seriously than what has been suggested by studies relied on import-weighted aggregated tariffs.