We model merger control procedures as a process of sequential acquisition of information and compare US and EU procedures. In the US, the authorities do not have to justify their decision to require further information (issue a second request), whereas in the EU, the authorities face a different (enforceable) standard of proof in phase I relative to phase II. We find that in the absence of remedies, the US procedure is always superior in terms of expected consumer welfare. When we allow for remedies, we find that, compared to the US, merging parties in the EU have more scope to propose remedies in phase I that will preempt the authorities from uncovering unfavorable information in phase II, and this might reduce expected consumer welfare. However, the higher standard of proof in phase I can also in some circumstances act as a commitment not to accept remedies below some threshold and yield a higher expected consumer welfare in the EU. Our model also shows that for global mergers that have the same effect in the two jurisdictions, a decision to trigger a Phase II in the EU yields the same expected consumer welfare as a clearance in Phase I with remedies in the US. However, the converse is not true.
