Forthcoming

Using weighted concentration ratios for the entire economy, I argue that industrial concentration decreased in the U.S. from 1960 to the early 1980s and then began to increase. This rise in the last two decades of the 20 th century offsets any counteracting affects stemming from the growth of use of information technology in production or from imports and appears due primarily to the impact of the merger wave starting in the mid 1980s. I also consider briefly the relationship between increasing market concentration and a change in market competition, taking into account the expansion of e-commerce.