Cletus C. Coughlin and Thomas B. Mandelbaum explore several factors that may have produced these differences in states’ export growth. Using a technique called shift-share analysis, the authors determine that, in most cases, the industrial composition of a state's exports is not a major influence on its export growth. Rather, the relationship between export growth in a state's individual industries and national export growth in these industries causes state export growth to differ from the national average. Since previous research has established that capital abundance—especially human capital abundance—is the United States’ primary source of international comparative advantage, the link between a state's 1976-86 export growth and its growth in physical and human capital is also examined. When differences in the industrial mix of exports are eliminated, Coughlin and Mandelbaum find a positive relationship between a state's export growth and the growth of its human capital.