日本企業集團體制對投資效率的影響：雙層隨機邊界模型與最大模擬概似估計分析

Abstract

本論文探討日本企業所屬企業集團（keiretsu，又稱財團，直譯為「系列」）如何影響其投資效率。本文建構一個雙層隨機邊界模型（two-tier stochastic frontier model），以同時刻畫企業的投資不足與投資過度行為。企業集團成員可能因銀行較為保守的監督而出現投資不足，亦可能為了維繫借貸關係與銀行利潤而產生投資過度；同時，企業集團成員亦可能因與集團內銀行關係緊密，而較容易取得融資，從而展現較高投資效率。

模型採用最大模擬概似估計法（maximum simulated likelihood estimation）進行估計，並放寬傳統對無效率項分配的限制，允許其分別服從指數分配、半常態分配、Gamma 分配、Pareto 分配與 Weibull 分配。實證結果顯示，企業集團成員在 1990 年代以前的投資效率相對較高，但其後投資效率優勢逐漸消失，可能源於企業集團內部持續存在的殭屍放貸（zombie lending），以及其對銀行融資的持續依賴；相較之下，非企業集團企業則轉向市場導向的替代融資方式。

整體而言，研究結果突顯了在日本金融體系演變的過程中，銀行與企業關係的經濟意涵已發生顯著轉變。

This thesis examines how keiretsu affiliation influences investment efficiency in Japanese firms. A two-tier stochastic frontier framework is developed to capture both under- and over-investment. Keiretsu firms may under-invest due to conservative bank monitoring or over-invest to preserve lending relationships and bank profits; at the same time, close ties with group-affiliated banks may improve access to credit and enhance investment efficiency.

The models are estimated using maximum simulated likelihood estimation, relaxing standard distributional assumptions by allowing inefficiency terms to follow Exponential, Half-Normal, Gamma, Pareto, and Weibull distributions. The results show that keiretsu firms exhibited higher investment efficiency prior to the 1990s, but this advantage gradually dissipated thereafter, likely due to persistent zombie lending within keiretsu groups and continued reliance on bank financing, while non-keiretsu firms increasingly adopted market-based alternatives. The findings highlight the changing economic role of bank–firm relationships in Japan's evolving financial landscape.