This paper demonstrates the importance of using a flexible cost function specification when analyzing economies of scale and estimating the cost effect of banking mergers. The inflexibility of the translog cost function is illustrated and results are compared to more flexible spline and Fourier cost functions. Using these different approaches we predict the ex ante effect on average cost from mergers over 1987–1998 using a balanced panel of 130 Norwegian banks. On average mergers are predicted to lower costs. Predictions using the Fourier or spline approach are in overall agreement with computed actual average merger-cost changes ex post. Cost effects of electronic payments are also estimated and exceed cost reductions associated with mergers.

In providing financial services jointly, banks may reduce costs due to complementarities in production (cost economies of scope) or raise revenues from complementarities in consumption (revenue economies of scope). Cost economies of scope between bank deposits and loans have been found to be small. Revenue economies of scope are investigated here for the first time and found to be insignificant over 1978–1990 for both small and large banks and for those on or off the revenue-efficient frontier. The lack of complementarities between deposits and loans — where benefits are most likely to occur — suggests that claims of important synergies from an expansion of banking powers be taken with caution.