Diffusion of Innovations

History and Conceptual Overview of Diffusion

The study of the diffusion of innovations can be traced to the writings of Gabriel Tarde, a French sociologist and legal scholar. Tarde originated such key diffusion concepts as opinion leadership and the S-curve [Page 183]of adoption (although he did not use the same labels). Tarde's intellectual leads were followed up by anthropologists such as Wissler, who analyzed the diffusion of the horse among the Plains Indians. Wissler argued that adding horses to their culture led the Plains Indians, who had lived in peaceful coexistence, into a state of almost continual warfare with neighboring tribes.

The basic research paradigm for the diffusion of innovations emerged with Ryan and Gross's classic 1943 study of the diffusion of hybrid seed corn among Iowa farmers. This innovation was profoundly important, leading to increased corn yields of 20% per acre. The innovation had spread widely to Iowa farmers in previous years, but state administrators wondered why such an obviously advantageous agricultural technology required a dozen years to achieve widespread use. Ryan and Gross indicated that the average farmer needed 7 years to progress from initial awareness of the innovation to full-scale adoption (indicated by planting all of the corn acreage in hybrid seed), emphasizing how difficult it was for most individuals to adopt an innovation. Hybrid corn had to be purchased from a seed corn company, at a price per bushel not trivial to Iowa farmers in the Depression years. Further, adopting hybrid seed corn meant Iowa farmers had to discontinue their previous practice in which healthy ears of corn were used as seed for the following year.

During the 1950s many diffusion studies were conducted, particularly by rural sociologists, and they were directly influenced by the Ryan and Gross investigation. Meanwhile, the diffusion approach infected other social sciences, spreading to marketing, political science, and education. Everett M. Rogers in his classic 1962 book Diffusion of Innovations argued for a general model of diffusion, irrespective of discipline. Another key event leading to wider acceptance of the diffusion paradigm was Coleman, Katz, and Menzel's study of the diffusion among physicians of tetracycline, a new medical drug developed by Pfizer. Data were collected via personal interviews with virtually all of the medical doctors in four small communities in Illinois. Prescription data were also collected from pharmacies so the researchers knew the date when each doctor first prescribed the new drug. This represented an important methodological improvement—observed actual adoption—over the usual diffusion investigation, which depended upon respondent accuracy in recalling the date at which an innovation was adopted.

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