It will be difficult to measure without a clear definition. Perhaps, a taxonomy of definitions based on frequency of application would help so that important changes over small domains would be measured separately from unimportant changes over larger domains so that the rate of change in particle physics would a show a measure different from the development of robot vacuum cleaners. But once having determined clean definitions and categories, a simple count expressed as quantity per year, or other time frame, would give a rate. Those expressions could be used to compare a periods of time and determine if technological change was advancing.