Demand consolidation is widely used in pharmaceutical procurement to reduce prices, but it may also disrupt the supply structure by changing which firms can compete at the required scale, raising concerns about exclusion, concentration, and supply resilience. In this paper, I assemble new data on pharmaceutical procurement in Mexico to analyze who wins and who loses when procurement is conducted through consolidated purchases. I find that the supply structure is substantially disrupted. Exploiting variation that exposes products to consolidated purchases at different points in time, I find that consolidation disproportionately awards contracts to large firms and limits the participation of small firms to residual, non-consolidated purchases. This change in the composition of suppliers is accompanied by lower average prices, with a substantial decline in prices for consolidated contracts. Combining information from bids with a structural model of auctions, I find that these effects are consistent with the presence of economies of scale: higher volumes create a cost advantage for large firms, leading them to win most contracts.

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