"Fast-growing countries tend to experience rapid export growth with little secular change in their terms of trade. This contradicts the standard Armington trade model, which predicts that fast-growing countries can experience rapid export growth only to the extent that they accept declining terms of trade. This paper generalizes the monopolistic competition trade model of Helpman and Krugman (1985), providing a basis for growth-led exports without declining terms of trade. The key mechanism behind this result is that fast-growing countries are able to develop new varieties of products that can be exported without pushing down the prices of existing products. There is strong support for the new model in long-run export growth of many countries in the post-war era"--Federal Reserve Board web site.