報告書番号

Y02010

タイトル（和文）

投入要素単価水準を考慮した日米電気事業の効率性比較

タイトル（英文）

Comparison of DEA Efficiency and Input Factor Prices among Japanese and US Utilities

概要 （図表や脚注は「報告書全文」に掲載しております）

わが国の電気料金が国際的に割高である理由の一つとして、日本の電気事業者の非効率が原因ではないか、との指摘がある。これに対し、当所のデータ包絡分析法（Data Envelopment Analysis : DEA）を用いた日米電気事業の効率性比較分析では、効率性以外の要因、特に投入要素単価の日米格差が料金格差の原因と考えてきた。しかしこれまでのDEAモデルでは、投入要素単価水準の格差を考慮することはできなかった。本稿では比較的最近までのデータを用いて日米のDEA効率性を計測するとともに、DEAモデルを応用し、従来の計測では考慮されなかった単価水準についても分析に組込み、非効率と割高な単価水準が供給コストに与える影響について日米比較を行った。その結果、非効率がもたらす供給コストへの影響は20～30%で日米に大きな格差はない一方、日本の事業者は投入要素単価水準が高く、割高な単価水準が供給コストに与える影響は供給コストの30～40%であり、非効率がもたらす影響と比較すると最も格差の大きい年で約1.8倍となっている。米国については割高な単価水準の供給コストに与える影響は総じて10%程度であり、非効率が供給コストに与える影響の半分以下である。日米の供給コストの格差は、非効率の格差ではなく日本の投入要素単価水準の高さが主な要因と考えられる

概要 （英文）

It has been pointed out that Japanese electricity prices are much higher than those of other countries, and it is well known that reducing electricity prices is one of the purposes for introducing competition into the Japanese electric power industry. In order to reduce the electricity prices efficiently, it is necessary to verify the reasons for the high electricity supply costs. Several studies have been completed at CRIEPI that compare economic efficiency between Japanese and US utilities using Data Envelopment Analysis (DEA). These previous studies examined whether Japanese utilities were less efficient than those in the US and examined whether the high supply cost was caused by inefficiency. According to the results of these studies, Japanese utilities were more or equally efficient as compared to the US utilities, and the results could not support the hypothesis that the Japanese relatively high electricity supply cost was caused by the inefficiency of Japanese utilities.However, the previous studies didn’t take the levels of the input factor prices into consideration. Input prices are exogenously determined in DEA model calculations. Therefore some utilities were identified as efficient by the ordinary DEA model, even if they employed expensive input factors, and their supply cost were higher than the others. This study attempts to compare the inefficiency component of total supply costs in Japan and the US, and it also attempts to compare the high input factor prices component of total supply cost between two countries. The applied DEA model is used with newer data sets from 1992 to 2000. Furthermore, the effects of introducing retail competition on the utilities’ efficiency and supply costs are examined for the US utilities, by classifying the US utilities into two groups, utilities in restructuring active states (G1) and not in such states (G2). The results are as follows:1) The average efficiency level of Japanese utilities has been almost equal to the US average except in 2000. Several US utilities sold their power stations starting in 1998. While this fact contributed to improving their efficiency, the remaining US utilities improved their efficiency by reducing employees and raising the operating ratio of generation plants. As a result, the average efficiency of the US utilities rises from 1998 and exceeds that of Japanese utilities in 2000.2) This study uses the applied DEA model to clarify the influence of comparatively high input factor prices on Japanese and US electricity supply cost. In the applied model, the supply cost of each utility in the sample is compared to those utilities in the same sample that have similar cost share structures and the least expensive input factors. The index measured by this model can be easily compared with the influence of inefficiency on electricity supply cost.3) As a result, while the influence of inefficiency on supply cost is nearly similar between the two countries (around 30%), the influence of the comparatively high input prices of the Japanese utilities (30 ~ 40%) is much larger than that of the US utilities (around 10%). This result implies that the differential of electricity supply cost is caused by differential input prices, not inefficiency.4) According to the result of comparison between the US G1 and G2 utilities, the efficiency of the utilities in G2 group is higher than those of G1 group. Furthermore, the influence of comparatively high input prices is lower than those of G1. However since 1996, efficiency has been improving, and the influence of input prices have fallen down in G1 group. Therefore G1 group caught up with G2 group in 2000 in both efficiency and influence of input price level. These effects are caused by improving capital productivity and falling capital input prices for G1. Finally, improving labor productivity is observed in both groups.

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