Why Are Concavity Conditions Not Satisfied in the Cost Function? The Case of Japanese Manufacturing Firms during the Bubble Period*

This paper examines empirically the reasons why Japanese manufacturing firms frequently fail to satisfy concavity of the cost function in input prices. We focus on the ‘bubble period’ in the 1980s when land was in great demand and land prices soared. By estimating the translog cost function with land as one of production inputs, we find that violation of concavity mainly resulted from weak bank–firm relationship and massive transactions of land. We also demonstrate that elasticities of substitution between land and other inputs are estimated quite differently if the firms violating concavity are not excluded from the analysis.