A common approach to merger simulations used in antitrust cases is to calibrate demand from market shares and a few additional parameters. When the products involved in the merger case are differentiated along several dimensions, the resulting diversion ratios may be very different from those...

Farrell and Shapiro proposed a simple test of the possible upward pricing pressure (UPP) following a merger. They showed that the test may give false negatives, that is, indicate that a merger may not give an UPP, while a more comprehensive test would indicate the opposite. We show that their...