States having different economic systems have correspondingly different national trading policies and practices; these differences aggravate the problems of foreign trade organization and impede the growth of the international market. The accepted principles and the national organization of foreign trade in developed market economies have important characteristics in common, as do the principles and organization of centrally planned economies; but the actual trading practices of a country in either group may vary according to whether the trading partner is a member of the same group or of a different one. In the case of the developed market and centrally planned economy countries there is in each case a certain basic similarity which facilitates trading relations. However, there is not the same general similarity of trading organization and practices among developing countries. They have some structural characteristics in common, such as a predominant share of primary goods in their exports and a generally low level of per capita income, but the types of economic and social organization in these countries vary widely.
In the case of the third main trading group, the developing countries, there is not the same general similarity of trading organization and practices. They have some structural characteristics in common, but the types of economic and social organization vary from almost pure market economies to almost full state ownership, so the institutional arrangements in the field of foreign trade also differ widely.