Field of study specializes individuals’ human capital in ways that might be either substitutable or complementary to technological change. We study changes in the earnings distribution of the college-educated population between 1993 and 2010 using the National Survey of College Graduates. After documenting changes that increase earnings inequality, we decompose them into composition and wage-structure effects. We find that composition effects account for virtually none of the growth of inequality and, in fact, are surprisingly small, even after we incorporate field of study into the decomposition. We conclude with speculation about why large inter-field changes in earnings did not lead to comparable changes in the flow of entrants.