We use transaction-level data to study changes in the concentration of US imports. Concentration has fallen in the typical industry, while it is stable by industry and origin country. The fall in concentration is driven by the extensive margin: the number of exporting firms has grown, and the...

We use transaction-level data to study changes in the concentration of US imports. Concentration has fallen in the typical industry, while it is stable by industry and country of origin. The fall in concentration is driven by the extensive margin: the number of exporting firm has grown, and the...

We present a factor-proportions trade model in which heterogeneous firms can offshore intermediate inputs subject to fixed offshoring costs. In the skill-abundant country, high-productivity firms offshore a larger range of labor-intensive inputs to the labor-abundant countries than...