The study looked at how common ownership among private companies affects the best way to privatize public firms. They used a model where a public firm competes with private firms under common ownership. Depending on the private firms' costs, the best privatization policy can either increase, decrease, or follow an inverted U-shaped relationship with common ownership. If private firms have constant costs, the best policy decreases with common ownership. But if private firms' costs increase, any of the three patterns can happen. This shows that the best way to privatize a public firm depends on how the private firms' costs are structured.