BT/EE Merger: the importance of market definition

(by Richard Cadman) Last Friday, the Competition and Markets Authority (CMA) gave unconditional approval to the acquisition by BT, the UK’s largest fixed telecommunications provider, of EE, its largest mobile communications provider.  The CMA concluded, after a nine-month long investigation, that the merger would not lead to a Substantial Lessening of Competition (SLC) and that neither the wholesale nor retail customers of both companies would suffer any harm from the merger.  How much did this depend on product market definition?