Economists have long debated the relationships between market structure of banking sector and the profitability. General consensus asserts that more concentrated market is associated with higher profitability: banks with higher market share generally achieve higher profits. This empirical evidence can however hinge on two opposite explanations: in the first case banks increase their market share (via mergers and acquisitions) in order to exploit the resulting stronger market power and impose higher prices to their clients; the second explanation tells that more cost-efficient banks are able to lower the prices applied to their clients and therefore to gain new clients and finally enlarge their market share. In both cases there is a positiv...