Everett M. Rogers, Diffusion of Innovations,
4th Ed., New York: Free Press, 1995
The Ryan and Gross (1943) study of the diffusion of hybrid seed corn in Iowa is the most influential diffusion study. The hybrid corn investigation includes each of the four main elements of diffusion that we have just discussed, and serves to illustrate these elements.
The innovation of hybrid corn was one of the most important new agricultural technologies when it was released to Iowa farmers in 1928. The new seed ushered in a whole set of agricultural innovations in the 1 through the 1950s that amounted to an agricultural revolution in farm productivity. Hybrid seed was developed by agricultural scientists at Iowa State University and at other state land-grant universities. The diffusion of hybrid seed was heavily promoted by the Iowa Agricultural Extension Service and by salesman from seed corn companies. Hybrid corn yielded about 20 percent more per acre than the open-pollinated varieties that it replaced. It was also more drought-resistant and better suited to harvesting with mechanical
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corn-pickers. The seed lost its hybrid vigor after the first generation, so farmers had to purchase hybrid seed each year. Previously farmers had saved their own seed, selected from their best-looking corn plants. The adoption of hybrid corn meant that an Iowa farmer had to make important changes in his corn-growing behavior.
When Biyce Ryan, fresh from his Ph.D. studies at Harvard University, arrived at Iowa State University in 1939, he chose hybrid corn as the innovation of study in his investigation of social factors in economic decisions. This interest drew him to study how an Iowa farmer’s social relationships with his neighbors influenced the individual’s decision to adopt hybrid corn. Ryan had read anthropological work on diffusion while he was at Harvard, so he cast his Iowa study of hybrid corn in a diffusion framework. But un like the qualitative methods used in anthropological studies of diffusion, the Iowa investigation mainly utilized quantitative data from survey interviews with Iowa farmers about their adoption of hybrid corn seed.
In the summer of 1941, Neal Gross, a new graduate student in rural sociology, was hired as a research assistant on the hybrid corn diffusion project. Ryan and Gross selected two small Iowa communities located west of Ames, and proceeded to interview personally all of the farmers living in these two systems. Using a structured questionnaire, Neal Gross, who did most of the data gathering, interviewed each respondent as to when he decided to adopt hybrid corn (the year of adoption was to become the main dependent variable in the data analysis), the communication channels used at each stage in the innovation-decision process, and how much of the farmer’s corn acreage was planted in hybrid (rather than open-pollinated seed) each year. In addition to these recall data about the innovation, the two rural sociologists also asked each respondent about his formal education, age, farm size, income, travel to Des Moines and other cities, readership of farm magazines, and other variables that were later correlated with innovativeness (measured as the year in which each farmer decided to adopt hybrid corn).
Neal Gross was from an urban background, and initially felt somewhat uncomfortable interviewing Iowa farmers. Someone in Ames told Gross that farm people got up very early in the morning, so on his first day of survey data gathering, he arrived at a respondent’s home at 6:00 AM, while it was still half-dark. By the end of the day, Gross had interviewed twenty-one respondents, and he averaged an incredible fourteen interviews per day for the entire study! Today, a survey interviewer who averages four interviews per day is considered hard-working. During one personal interview, an Iowa
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farmer asked Gross for advice about controlling horse nettles. Gross had never heard of horse nettles. He told the farmer that he should call a veterinarian to look at his sick horse (horse nettles are a kind of noxious weed).
Neal Gross personally interviewed 345 farmers in the two Iowa communities, but twelve farmers operating less than twenty acres were discarded from the data analysis, as were seventy-four respondents who started farming after hybrid corn began to diffuse. Thus, the data analysis was based on 259 respondents.
When all the data were gathered, Ryan and Gross coded the farmers’ interview responses into numbers. The diffusion researchers analyzed the data by hand tabulation and with a desk calculator (computers were not available for data analysis until some years later). Within a year, Neal Gross (1942) completed his Master’s thesis on the diffusion of hybrid corn, and shortly thereafter Ryan and Gross (1943) published their research findings in the journal, Rural Sociology (this article is the most widely cited publication from the study, although there are several others).
All but two of the 259 farmers had adopted hybrid corn between 1928 and 1941, a rather rapid rate of adoption. When plotted cumulatively on a year-by-year basis, the adoption rate formed an S-shaped curve over time. After the first five years, by 1933, only 10 percent of the Iowa farmers had adopted. Then, the adoption curve “took off,” shooting up to 40 percent adoption in the next three years (by 1936). Then the rate of adoption leveled off as fewer and fewer farmers remained to adopt the new idea.
Farmers were assigned to adopter categories on the basis of when they adopted the new seed (Gross, 1942), Compared to later adopters, the innovators had larger-sized farms, higher incomes, and more years of formal education. The innovators were more cosmopolite, as measured by their number of trips to Des Moines (Iowa’s largest city, located about seventy- five miles away).
Although hybrid corn was an innovation with a high degree of relative ad vantage over the open-pollinated seed that it replaced, the typical farmer moved slowly from awareness-knowledge of the innovation to adoption. The innovation-decision period from first knowledge to the adoption-decision av eraged about nine years for all respondents, a finding that the innovation decision process involved considerable deliberation, even in the case of an innovation with spectacular results. The average respondent took three or four years after planting his first hybrid seed, usually on a small trial plot, be fore deciding to plant 100 percent of his corn acreage in hybrid varieties.
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Communication channels played different roles at various stages in the innovation-decision process. The typical farmer first heard of hybrid seed from a salesman, but neighbors were the most frequently cited channel leading to persuasion. Salesmen were more important channels for earlier adopters, and neighbors were more important for later adopters. The Ryan and Gross (1943) findings suggested the important role of interpersonal net works in the diffusion process in a system. The farmer-to-farmer exchange of their personal experiences with hybrid seed was at the heart of diffusion. When enough such positive experiences were accumulated by the innovators and early adopters, and exchanged with other farmers in the community, the rate of adoption took off. This threshold for hybrid corn occurred in 1935. After that point, it would have been impossible to halt the further diffusion of hybrid corn. The farm community as a social system, including the networks linking the individual farmers within it, was a crucial element in the diffusion process.
In order to understand the role of diffusion networks and opinion leadership, Ryan and Gross (1943) should have asked sociometric questions of their respondents, such as, “From which other farmers have you obtained information about hybrid corn?” The sample design, which consisted of a complete enumeration in two communities, would have made the use of sociometric questions appropriate. But “information was simply collected from all community members as if they were unrelated respondents in a random sample” (Katz and others, 1963).
Even without sociometric data about diffusion networks, Ryan and Gross (1943) sensed that hybrid corn spread in the two Iowa communities as a kind of social snowball: “There is no doubt but that the behavior of one individual in an interacting population affects the behavior of his fellows. Thus, the demonstrated success of hybrid seed on a few farms offers new stimulus to the remaining ones.” The two rural sociologists intuitively sensed what later diffusion scholars were to gather more detailed evidence to prove: That the heart of the diffusion process consists of interpersonal network exchanges and social modeling between those individuals who have already adopted an innovation and those who are then influenced to do so. Diffusion is fundamentally a social process.
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Study of the invisible college of rural sociologists investigating diffusion as of the mid-1960s identified the researchers who first utilized a new concept and/or methodological tool in studying diffusion (Crane, 1972). Ryan and Gross launched fifteen of the eighteen most widely used intellectual innovations in the rural sociology diffusion research tradition. So Bryce Ryan and Neal Cross played key roles in forming the classical diffusion paradigm. The hybrid corn study has left an indelible stamp on the history of diffusion research.
This case illustration is based on Ryan and Gross (1943), Gross (1942), Ryan and Gross (1950),and Valente and Rogers (1994).
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Summary (a portion of Everett Roger’s summary of his theory of diffusion)
Diffusion is the process by which an innovation is communicated through certain channels over lime among the members of a social system. Diffusion is a special type of communication concerned with the spread of messages that are perceived as new ideas. Communication is a process in which participants create and share information with one another in order to reach a mutual understanding. Diffusion has a special character because of the newness of the idea in the message content. Thus some degree of uncertainty is involved in the diffusion process. An individual can reduce the degree of uncertainty by obtaining information. Information is a difference in matter-energy that affects uncertainty in a situation where a choice exists among a set of alternatives.
The main elements in the diffusion of new ideas are: (1) an innovation, (2) which is communicated through certain channels, (3) over time, (4) among the members of a social system. An innovation is an idea, practice, or object perceived as new by an individual or other unit of adoption. Almost all of the new ideas discussed in this book are technological innovations. A technology is a design for instrumental action that reduces the uncertainty in the cause-effect relationships involved in achieving a desired outcome. Most technologies have two components: (1) hardware, consisting of the tool that embodies the technology as a material or physical object, and (2) software, consisting of the knowledge base for the tool.