Departmental Bulletin Paper パラメトリックな確率的生産フロンティアへの環境要因の影響 : 水道事業の不均質性と不均一分散へのSFAの適用
The Impact of Environmental Factors on Parametric Stochastic Production Frontier: Application of SFA to Heterogeneous and Heteroskedastic Data of Japanese Water Utilities

矢根, 遥佳  ,  矢根, 真二

The purpose of this paper is to examine the effects of environmentalvariables on the production frontier and technical efficiency usingstochastic frontier analysis (SFA). In order to do so, this study applies threekinds of one-step models to Japanese water utilities, which areheterogeneous and heteroskedastic. These models take the mean andvariance of the one-sided error term (which indicates inefficiency) intoconsideration. The main conclusions are as follows: 1) based on the resultsfrom log-likelihood ratio test, Wang (2002)’s model is chosen; 2) estimationsthat fail to acknowledge environmental variables cause bias in theestimates of the production frontier and technical efficiency; 3)environmental variables intake capacity, consumer density, load ratio,purchased water ratio and well water ratio have a positive impact, lowwater quality, subsidy ratio and price level have a negative effect onefficiency level; and 4) the traditional two-step method cannot sufficientlyaccount for the effects of these environmental variables.

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