Implementing the Hypothetical Monopolist SSNIP Test with Multi-Product Firms

This note describes the implementation of the hypothetical monopolist ssnip test for market definition in the context of merger cases where firms produce multiple differentiated products. The test developed here represents an extension and generalization of the Katz-Shapiro and O'Brien-Wickelgren market definition test for the case of multi-product firms. We present and explain this test with an illustrative example. In the Appendix, we provide a more general and technical description of the test