Welfare Effects of Buyer and Seller Power

In this paper, we provide a theoretical characterization of the welfare effects of buyer and seller power in vertical relations and introduce an empirical approach for quantifying the contributions of each channel to deadweight loss. Our model accommodates both monopsony distortions from buyer power and double-marginalization distortions from seller power. Rather than imposing a specific form of vertical conduct, we allow it to arise endogenously based on model primitives. We show that the relative elasticity of upstream supply and downstream demand is the key determinant of whether buyer or seller power creates distortions. Applying our framework to coal procurement by power plants in Texas, we find that 83% of the distortion comes from the monopoly power of coal mines, with the remainder attributed to the monopsony power of power plants.