22 Krugman/Obstfeld/Melitz • International Economics: Theory & Policy, Tenth Edition
The chapter begins by developing a general equilibrium model of an economy with two goods that are
each produced using two factors according to fixed coefficient production functions. The assumption of
fixed coefficient production functions provides an unambiguous ranking of goods in terms of factor
intensities. (A more realistic model allowing for substitution between factors of production is presented
later in the chapter with the same conclusions.) Two important results are derived using this model. The
first is known as the Rybczynski effect. Increasing the relative supply of one factor, holding relative goods
prices constant, leads to a biased expansion of production possibilities favoring the relative supply of the
good that uses that factor intensively.
The central message concerning trade patterns of the Heckscher-Ohlin theory is that countries tend to
export goods whose production is intensive in factors with which they are relatively abundantly endowed.
Comparing the United States and Mexico, for example, we observe a relative abundance of capital in the
United States and a relative abundance of labor in Mexico. Thus, goods that intensively use capital in
production should be cheaper to produce in the United States, and those that intensively use labor should
be cheaper to produce in Mexico. With trade, the United States should export capital-intensive goods like
After presenting the basic theory behind the Heckscher-Ohlin theory, the rest of the chapter examines empirical
tests of the model, beginning with a pair of case studies looking at income inequality in the United States.
Wages paid to skilled workers in the United States have been rising at a much faster rate than those paid to
unskilled workers over the past few decades. At the same time, there has been a large increase in
international trade. Given that the United States is relatively abundant in skilled labor, the Heckscher-