Growing Oligopolies, Prices, Output, and Productivity

American industries have grown more concentrated over the last 40 years. In absence of productivity innovation, this should lead to price hikes and output reductions, decreasing consumer welfare. With US census data from 1972 2012, I use disentangle revenue output. Industry-level estimates show that concentration increases are positively correlated real growth, uncorrelated with changes overall payroll, negatively labor’s share. rationalize these results in a simple model competition. Productive (with growing oligopolists) expand hold down prices, raising welfare, while maintaining or reducing their workforces, lowering share (JEL D43, L13, D24, D33, D21, D42)