This paper provides evidence on the empirical separability of input and output market imperfections. We specify a model of banking competition and simultaneously estimate bank conduct in output (loan) and input (deposit) markets. Our results suggest that firms display some degree of non-competitive behavior in both the loan and the deposit markets. Moreover, we find that the input side and the output side are empirically separable, that is, the measurement of market power on one side of the market is not affected by assuming that the other side of the market is perfectly competitive. Our results suggest that empirical studies of market power that concentrate on either the input side or the output side are not subject to significant misspecification error.