Mergers between large firms have profound impacts on smaller firms. When two big companies join forces they typically drive prices up for customers and control a large portion of the market, making it more difficult for smaller firms to enter the market and compete. However, not all mergers have a negative effect on the entry and proliferation of smaller firms. For instance, the 2007 MillerCoors joint venture (between SABMiller and Molson Coors) inadvertently increased the number of smaller craft brewers in the market. José Azar at the University of Navarra and I examined the effect of the MillerCoors merger in a research paper published in the International Journal of Industrial Organization. We found that the merger between two large commercial brewers created an opening for independent brewers to enter the market and gain market share. Craft brewers seized the opportunity to differentiate themselves by offering specialised products and a new experience.