We study the welfare costs of markups in a dynamic model with heterogeneous firms and endogenous markups. We provide aggregation results summarizing the macro implications of micro-level markup heterogeneity. We calibrate our model to US Census of Manufactures data and find that the costs of markups can be large. We decompose the costs into three channels: an aggregate markup that acts like a uniform output tax, misallocation of factors of production, and inefficient entry. We find that the aggregate-markup and misallocation channels account for most of the costs of markups and that the entry channel is much less important.

We document strong skill matching in Turkish firms’ production networks. Additionally, in the data, export demand shocks from rich countries increase firms’ skill intensity and their trade with skill-intensive domestic partners. We explain these patterns using a quantitative model with heterogeneous firms, quality choices, and endogenous networks. A counterfactual economy-wide export demand shock of 5% leads both exporters and nonexporters to upgrade quality, raising the average wage by 1.2%. This effect is nine times the effect in a scenario without interconnected quality choices. We use the model to study the conditions for the success of export promotion policies.