TECHNOLOGY MAPPING AND THE EVALUATION OF TECHNICAL CHANGE

In this paper a model of technological evolution based on a twin chara cteristics representation and on a population approach has been used t o discuss the possibility of obtaining a single measure of technical c hange which could be used for all possible types of evaluation. Possib le changes for a technological population include changes in position, changes in density, corresponding to a change in the intensity and ty pe of competition; changes in the shape of the technological populatio n corresponding to the formation of particular trajectories, or to the fragmentation of an existing population following from a process of s pecialization. In view of these evolutionary trends it is considered i mpossible to obtain a unique measure of technological change which is useful for all types of evaluation. The heterogeneity/dispersion of th e technological population and the presence of qualitative change limi t the accuracy and the meaning of measurements of technical change. Th is means that only in particular circumstances (e.g. long periods of o bservation and populations of unchanging shape, or developments along a particular trajectory) would such measurements be reasonably accurat e and meaningful.