Economies of scope in the Japanese banking industry

Economies of scope are usually considered a key factor in explaining bank diversification benefits, as joint production can help spread costs across different operations. However, previous studies have yielded little evidence of scope economies in the banking sector, which fails to explain the empirical results of diversification benefits, especially in Japan. Given that most relevant studies were conducted prior to 2000 and newer methodological approaches have emerged to enhance estimation accuracy, we refocus to this topic and explore the relationship with bank diversification. In this paper, we estimate economies of scope while considering the growing off-balance sheet activities within the Japanese banking industry. Using a sample including 120 Japanese banks from 2000 to 2020, we estimate the cost frontier with a translog cost function through the stochastic frontier analysis (SFA) approach. In addition to the traditional measures, we incorporate a new measure of scope economies proposed by Chavas and Kim (2010), allowing us to decompose the scope economies into four different effects. Our findings suggest that nearly all Japanese banks exhibit economies of scope, which may explain the diversification benefits observed in Japan. Furthermore, we find a negative relationship between economies of scope and the level of bank diversification.