A number of formerly regulated multiproduct industries have a transitional or permanent residual regulatory mandate to protect consumers from "excessive" prices. The legislation that deregulated most rail rates contains a statutory mandate for the regulator to protect shippers from "excessive"...

Concentration-based screens for horizontal mergers, such as those employed in the US DOJ and FTC Horizontal Merger Guidelines, play a central role in merger analysis. However, the basis for these screens, in both form and level, remains unclear. We show that there is both a theoretical and an...