The book "The Microsoft Antitrust Cases. Competition Policy for the Twenty-First Century," written by Andrew I. Gavil and Harry First, is an excellent account of the cases that several jurisdictions and institutions brought against Microsoft since the end of the twentieth century for abuse of its dominant position. The book contains a chapter that praises the role of institutional diversity in these cases. The conclusion of this chapter (which has lessons for Spain, a jurisdiction that in the recent past has reduced institutional diversity by merging regulatory and anti-trust agencies) is this:
"The arguments for a diverse and decentralized system of antitrust enforcement go beyond history and the steps that agencies have taken to manage the system in which they operate. There are good theoretical arguments for why decentralization produces benefits for antitrust enforcement: it can encourage policy diversity and experimentation, it can expand resources devoted to investigation and enforcement, and it can shadow the decentralized federal government structure into which it fits. The system is further supported by the process of institutional competition that multiple enforcement creates -processes that can help check enforcement abuses and give agencies positive incentives to produce good results.
The benefits predicted by theory are borne out to a large degree in the Microsoft litigation. Looking at the litigation from its earliest genesis at the Federal Trade Commission to its more recent conclusion in Europe, it is hard to imagine a better result had one agency been in charge. Multiple agencies, with different strengths, different legal instruments, and different policy views, were necessary to produce the benefits to competition law that the Microsoft litigation produced. There were many aspects of the litigation and remedy to criticize, as our earlier chapters indicate. But our diverse system of antitrust enforcement isn't one of them."