We show how production and pricing data can be used to estimate merger-related efficiencies using pre-merger data, and we assess the changes in efficiency and marginal costs that are expected to occur post-merger. To do this, we jointly estimate firm level returns to scale, technical change, TFP growth, and price-cost markups. We implement our empirical model using data for the North American (US and Canadian) brewing industry, and we use the estimated model of firm technology to evaluate the changes that are associated with the merger between Molson and Coors. We forecast nontrivial increases in returns to scale and declines in marginal costs and we verify those results by analyzing the impact of the merger retrospectively using post-merger data.