The pace of Japanese economic growth was substantially higher than that exhibited by the group of developed economies between 1985 and 1995; later has been lower. What explains this relative decline? According to the econometric results of an exercise carried out, inspired by the model of Aghion and Howitt (2009), the hypotheses of insufficient investment or savings can be considered implausible to explain such performance, while an alternative hypothesis can be considered likely: The loss of efficiency of the Japanese society, compared with the other developed societies, to transform resources required in R&D into a high and constant rate of technical change.