How do innovations (defined as idea, products, and practices perceived as new by an individual) diffuse to members of a social system? The authors answer this and other questions about the character of innovators, the rate of adoption of ideas, and the decision-making process in 103 generalizations about diffusion of innovation. These propositions are synthesized from more than 1,500 publications dealing with the communication of innovations. The new ideas they studied range from tractors in Turkey, to family planning techniques among Hindu housewives, to modern math among Pennsylvania teachers. The book is an up-date of a 1962 edition, which places its emphasis on cross-cultural perspectives and the concepts and theories in communication and social psychology. An extensive bibliography of approximately 1200 empirical reports and about 300 non-empirical reports is appended. (JY)