In some economic analyses， productivity ls estimated by input data defined by tangible resources such as labor and capital stocks． For industrial growth， however， firms need not only tangible resources but also intangible ones． In the pharmaceutical industry， research and development（R＆D）investment is acritical expenditure affecting future productivity． The future return to R＆D investment is generated by future inventions；in other words， present R＆D investment provides the source of new technology and new products． In addition， new products and new technologies require accumulation of the results of R＆D investment． That is the intangible asset called knowledge capital stock． In this paper， I estimate marginal capital productivity from the view of intan・ gible capital stocks． I found that the marginal capital productivity of both tangible capital and knowledge capital have been falling steadily over a number of years．研究ノート(Note
