Article ID: 0190403a
Since the 1990s, research has been done on lean production systems with progressive development of a scale for measuring characteristic leanness in efficient production organizations. For example, Shah and Ward (2003, 2007) originated from the HPM and IMSS surveys become as the de facto standard. However, the explanations of these studies were not necessarily convincing. In contrast, in the IMVP survey, site visits were made to automakers’ development and production genba or sites in each country surveyed, in addition to the use of questionnaires. However, in actuality, a comparison of multiple Japanese automakers showed differences in methods and means for achieving just-in-time production in organizations, even at the genba that would be believed to score high on a leanness scale, such as JIT production. It is difficult to detect and measure these differences through large-scale cross-industry questionnaire surveys alone, and there is a possibility that this difficulty manifests in the weak explanatory power of the lean studies. Approaches to explaining differences in performance using “leanness scale” are based on a lean hypothesis where there is a best practice lean situation transcending nations and industries, yet its low explanatory power creates suspicion with regard to the validity of this hypothesis.