Skills and changing comparative advantage

Using U.S. input-output data for the period 1947-1996 and Dictionary of Occupational Titles skill scores, I find that U.S. exports have a high content in cognitive and interactive skills relative to imports, and a low content in motor skills. Moreover, the skill gap between exports and imports has widened over time. Imports are more capital- and equipment-intensive than exports, but the difference has fallen over time. By 1987 exports were more computer-intensive than imports. In contrast, though exports were more R & D-intensive than imports in 1958, they were slightly lower in 1996. Labor productivity also rose faster in export than in import industries, and the unit labor cost of exports declined relative to imports.