The effects of trade and trade policy on developing countries may be different from those on developed countries, and developing countries may want different benefits from trade, and various forms of special and differential treatment have been used (and suggested) to meet these differences. The changes in theories of development, in what is 'normal' treatment in trade, and in the types of countries now found in the categories 'least developed' and 'developing' require a re-examination of the objectives and tools.