Since the end of the Second World War considerable efforts have been made to reduce the barriers to world trade, with some success in the field of manufactures, but very little in the field of primary products. Such efforts were badly needed after the catastrophic decline in world trade during the depression of the 1930S and the detailed controls over trade that were wide spread during and immediately after the Second World War. The gradual reduction of detailed controls over international payments has been facilitated by the operation of the International Monetary Fund (especially in the matter of controls over invisible items and capital movements); whilst the operation of the Organization for European Economic Co-operation did much to encourage countries to remove quantitative controls within Europe in the earlier post-war years, and tariff barriers have also been greatly reduced during a series of negotiations under the terms of the General Agreement on Tariffs and Trade (,Gate). The general principle of these tariff reductions was that new preferences would not be given by one country to another, and that any reduction in a member's tariffs had therefore to apply to its imports from all member countries (,most-favoured nation treatment') unless the cuts were made in the course of setting up a customs union or a free trade area.