'Merger Control' refers to the procedure of reviewing mergers and acquisitions under antitrust / competition law. Over 60 nations worldwide have adopted a regime providing for merger control.

Merger control regimes are adopted to prevent anti competitive consequences of concentrations. Accordingly most merger control regmines provide for one of the following substantial tests:

Does the concentration

• substantially lessen competition? (US, UK)

• substantially impede competition? (EU)

• lead to the creation or strenghthening of a dominant position? (Germany, Switzerland)

In practice most standards have very similar underlying principles in common. Simplified, the creation of a dominant position would usually result in a substantial lessening or impedement of competition.

While it is undisputable that a concentration may lead to a reduction in output and result in higher prices and thus in a welfare loss to consumers, the antitrust authority faces the challenge of applying various economic theories and rules in a legally binding procedure.

Modern merger control regimes are of an ex-ante nature giving the authority the right to block a concentration pending the review procedure. The antitrust authority thus has the burden of predicting the anti-competitive outcome of a concentration. However, an ex-ante regime has proven to be far more effective in preventing anticompetitive concentrations, as it would be almost unfeasible to unravel consummated concentrations afterwards.