The more merchants that take cards, for example, the more benefit there is to holding a card. And the more people that hold cards, the more benefit there is to merchants accepting cards. The network effect is both what can make it difficult for new systems to get off the ground and also entrench large networks.
Central bank transparency and accountability  The independence of a central bank, especially in democracies, must be accompanied by the bank’s responsibility to account for its policies and the achievement of its objectives. For that purpose it is necessary to provide it with clearly defined targets against which its performance can be measured.