T HE theoretical role of technology in economic growth is no mystery. It provides new machines and processes (improved capital quality) that raise output relative to input, or productivity. Yet for several reasons, once it comes to pursuing this truth by observation, hypothesis, and testing, every manner of obstacle seems to appear. One may be told that technology per se is rarely susceptible of measurement, that productivity increases can be attributed to many causes, impossible to untangle, or that the precise link between embodied technological change and productivity is too hazy. Such doubts are often justified. At times, however, they may unduly discourage those whose curiosity is not satisfied by aggregate production functions, and who would prefer to investigate more closely some particular reasons for productivity increases. To be clear on this point, technological innovation frequently is difficult to represent quantitatively. Output per unit of input often does rise for non-technological reasons (economies of scale, changes in rates of utilization of capacity, or optimal factor combinations), but there must be important cases where the reverse is true. One such case seems to be electrification of manufacturing industries. Here the rate of technical change can be reasonably well measured in terms of horsepower capacity of power equipment and consumption of power (work output). Furthermore, this revolution in the application of power can be viewed against the background of clear, known changes in manufacturing productivity changes which remain mostly unexplained. Specifically, it might be expected that there would be a relationship between electrification and reduced costs of production.' More broadly, the case of electrification might illustrate how the quantitative link between technological change and productivity can be developed. To this end, what follows (section I) traces some suggestive findings regarding the rise of electric power and changes in productivity in American manufacturing, and (section II) attempts to construct a theoretical framework for measuring the impact of electrical technology on factor costs. It is hoped that section II will help shed more light upon the broader question mentioned above, by providing procedures that could be adapted to a wide range of technologyproductivity cases.