Increases in import competition led to large increases in labor productivity growth in highly concentrated industries during the period from 1975 through 1987. The finding is based on a panel of ninety-four manufacturing industries observed over four periods, each of three years duration. Imports had no observable effects on productivity growth in less concentrated industries; the strong effects in concentrated industries did not occur contemporaneously but appeared with a one-period lag. The effects are weakened but still statistically significant when Bureau of Labor Statistics productivity data are replaced by National Bureau of Economic Research data and in a larger panel with less precise trade data. Copyright 1994 by MIT Press.

The pattern of diversification within U.S. manufacturing between 1963 and 1977 are examined. Firms didn't diversify at random; they were more likely to enter rapidly growing industries, and industries that were related to their primary activities through supply relationships or marketing similarities. Research and development (R & D) expenditures also influence the observed patterns. R & D intensive industries generate outbound diversification and attract inbound diversification. However, the strongest influence is directional; R & D intensive firms channel their diversification toward R & D intensive industries. Much diversification reflects the transfer of sharable organization capital among related activities.