Sorry, I don't have an easy anwer. In order to get an insight best look for introductory chapters in monographs on „Innovation diffusion“ or textbooks on „Innovation*“
Could also look at this reference - a bit old now though
Holland, Matt, ‘Diffusion of Innovation Theories and Their Relevance to Understanding the Role of Librarians When Introducing Users to Networked Information’, The Electronic Library, 15 (1997), 389-394 .
Adoption index: measures the extent of adoption at the time of the survey. It is used in the case of study of multiple practices to measure adoption and intensity of adoption of improved production packages at the time of the survey.