This article aims at investigating the efficiency of European and US commercial banks. Scale and scope economies indicators, as well as a measurement of X-efficiency are derived from three cost functions: Fourier flexible form, translog and Box-Cox. This allows checking the stability and the robustness of the evidence across the different specifications. Our results over the period 1995-98 show that, overall, the largest banks do not seem to have higher efficiency scores. Therefore, further enlargement of the production size does not necessarily lead to production gains.
