Who Should Copy Whom in the Design of Merger Control?

(by Bruce Lyons) The UK regime for controlling potentially anticompetitive mergers has a number of idiosyncrasies as compared with most other competition authorities across the globe.  For example:  the two phases of merger inquiries are carried out by separate institutions; merger notification is voluntary;  very small mergers can be caught by the ‘share of supply’ test for jurisdiction; and minority shareholdings can be prohibited on the grounds of ‘material influence’.  Some of these are good idiosyncrasies, and other jurisdictions could learn from the UK, but other idiosyncrasies are a handicap, and the UK system would benefit from reform.  Which fall into each of these two categories?