| Abstract: | A theory of oligopolistic innovation adoption is developed in which intrafirm diffusions occur because the marginal cost of adoption is increasing in the rate of adoption. The equilibrium intrafirm diffusion curve is S-shaped or concave, as are empirically observed ones. This diffusion curve is more likely to be S-shaped the more competitive the industry, the larger the marginal cost of adoption or the pre-innovation unit cost of production, or the smaller the demand. The diffusion is longer, and so the extent of adoption at any date is lower the more competitive the industry, the larger the marginal cost of adoption or the pre-innovation unit cost of production, or the smaller the demand. A surprising result is that an increase in the unit cost reduction from the innovation has an ambiguous effect on diffusion. Obviously, a larger cost reduction allows each firm to earn a larger flow profit at every date from the same rate of adoption. However, a more subtle effect is that it also allows the firm to earn the same flow of profit with a slower rate of adoption, and so lower adoption costs. That is, the firms also have an incentive to spread out the diffusion over a longer period of time to save on adoption costs. |
