Kazuo Sato (1927–2004) contributed a great deal to index number theory, theory of production structure and the contemporary state of the Japanese economy. He discovered an ideal formula for a log change index number, based on his deep understanding in the production structure. He anticipated many contemporary issues in Japan's macroeconomy: the Paasche bias in the GDP deflator, index number problems when industrial structures are under drastic changes, the potential output level or the output gap, and the role of culture on saving behavior. Moreover, in his quiet manner, he devoted himself to serve the academic community by editing the Japanese Economic Studies (now the Japanese Economy) by introducing and translating many important articles that had been published in English – a deed of thankless effort.