Paul Krugman - Academic Career - New Trade Theory

New Trade Theory

Prior to Krugman's work, trade theory (see David Ricardo and Hecksher-Ohlin model) emphasized trade based on the comparative advantage of countries with very different characteristics, such as a country with a high agricultural productivity trading agricultural products for industrial products from a country with a high industrial productivity. However, in the 20th century, an ever larger share of trade occurred between countries with similar characteristics, which is difficult to explain by comparative advantage. Krugman's explanation of trade between similar countries was proposed in a 1979 paper in the Journal of International Economics, and involves two key assumptions: that consumers prefer a diverse choice of brands, and that production favors economies of scale. Consumers' preference for diversity explains the survival of different versions of cars like Volvo and BMW. However, because of economies of scale, it is not profitable to spread the production of Volvos all over the world; instead, it is concentrated in a few factories and therefore in a few countries (or maybe just one). This logic explains how each country may specialize in producing a few brands of any given type of product, instead of specializing in different types of products.

Krugman modeled a 'preference for diversity' by assuming a CES utility function like that in a 1977 paper by Avinash Dixit and Joseph Stiglitz. Many models of international trade now follow Krugman's lead, incorporating economies of scale in production and a preference for diversity in consumption. This way of modeling trade has come to be called New Trade Theory.

Krugman's theory also took into account transportation costs, a key feature in producing the "home market effect", which would later feature in his work on the new economic geography. The home market effect "states that, ceteris paribus, the country with the larger demand for a good shall, at equilibrium, produce a more than proportionate share of that good and be a net exporter of it." The home market effect was an unexpected result, and Krugman initially questioned it, but ultimately concluded that the mathematics of the model were correct.

When there are economies of scale in production, it is possible that countries may become 'locked in' to disadvantageous patterns of trade. Nonetheless, trade remains beneficial in general, even between similar countries, because it permits firms to save on costs by producing at a larger, more efficient scale, and because it increases the range of brands available and sharpens the competition between firms. Krugman has usually been supportive of free trade and globalization. He has also been critical of industrial policy, which New Trade Theory suggests might offer nations rent-seeking advantages if "strategic industries" can be identified, saying it's not clear that such identification can be done accurately enough to matter.