57 Highly industrialized nations export their own manufactured products, for the most part. Less developed nations, on the other hand, have nothing to sell but raw materials and agricultural crops. As a result of technical progress, the price of manufactured products is rising rapidly and they find a ready market. But the basic crops and raw materials produced by the less developed countries are subject to sudden and wide-ranging shifts in market price; they do not share in the growing market value of industrial products. This poses serious difficulties to the developing nations. They depend on exports to a large extent for a balanced economy and for further steps toward development. Thus the needy nations grow more destitute, while the rich nations become even richer.
Source: Populorum Progressio (Vatican.va)