The Rate of Obsolescence of Technical Knowledge-A Note

A NUMBER of attempts to assess the size of the stock of technical knowledge have been made in recent years. Estimates of the U.K. stock are reported in Schott [I9, pp. 48-50], [20, pp. 90-7], based on a similar approach to that used by Wagner [22] and Kendrick [9]. The calculations not only require information about the rate at which new knowledge becomes available, but also about the rate at which existing knowledge becomes obsolete. While quite detailed data on the additions to the stock were available to previous authors, they possessed little or no information about the decay in the usefulness of existing knowledge. Schott [20, p. 96], for example, was forced to draw attention to 'our state of ignorance concerning the obsolescence rate of technical knowledge'. This note attempts to provide estimates of the rates of obsolence of existing technical knowledge for the U.K. The results reported below bring into question the assumptions adopted in other studies about the size of the annual rate and its constancy over time.