Time and the Rate of Adoption of Innovations

Rogers and Shoemaker (1971) define rate of adoption as "the relative speed with which an innovation is adopted by members of a social system. This rate of adoption is usually measured by the length of time required for a certain percentage of the members of a system to adopt an innovation" (p. 28). Rogers and Shoemaker agree with Toffler (1970) and others that the rate of adoption of innovations is rapidly increasing over time. For instance, they justify the need for their book with the opening statement that "the phenomenal rate at which innovations are being invented, developed, and spread makes it important to look at how these new ideas affect (or fail to affect) the existing social order (Rogers and Shoemaker 1971, p. 1). " But, no evidence is presented to show that the rate of adoption is increasing. A review of the research on adoption-diffusion of innovations identified only one study that explicitly tested this hypothesis. Mansfield (1961) investigated the extent of time it took firms in four different industries (bituminous coal, iron and steel, brewing, and railroads) to adopt 12 innovations (e.g., shuttle car, byproduct coke oven, tin container, and diesel locomotive). Noting that the hypothesis of increasing rates of adoption has been advanced by economists on several occasions, due to such factors as the evolution of better communication channels, more sophisticated techniques to evaluate machine replacement, and more favorable attitudes toward technological change, Mansfield found that "there is some apparent tendency for the rate of imitation to increase over time, but it is not statistically significant" (Mansfield 1961, p. 756). Only one study of changes in the rates of growth of consumer products was located, in the form of an unpublished paper by Young (1964). Young was interested in the "shortening" of the product life cycle over time and observed that for household appliances the rate of growth was rapidly increasing. He selected 30 electrical home appliances and divided them into three groups, based on year of introduction: before 1920; 1920-1939; 1939-1959. Young found that the average growth rate for each of the three groups was, respectively: 13 percent, 20 percent, and 50 percent. The average time required to reach the year of peak sales for each of the three groups was, respectively: 34 years, 22 years, and 8 years. Young's analysis provides strong evidence for his thesis that product life cycles are shortening due to rapidly accelerating technological developments. However, his results cannot be interpreted unequivocally as evidence for increases in the rate of adoption over time, because Young analyzed sales data and not penetration data. (Sales data include repeat and multiunit purchases.) The purpose of this study was to test explicitly the hypothesis that the rate of adoption of innovations in consumer markets is increasing over time. Although Mansfield (1961) found little evidence for this trend in industrial markets, Young's analysis strongly suggests that such a trend does exist in consumer markets. Furthermore, time was expected to be a significant "determinant" of rate of adoption of consumer products, i.e., improvements in channels of communication, increases in marketing sophistication, and increases in consumer affluence should lead to more rapid adoption of innovations.