The spatial diffusion of innovations

In a spatial context of diffusion, the geographical reach of externalities is a determinant of the spatial pattern of diffusion. In a spatial model, externalities are therefore physically local. In general, spatial diffusion theory stresses the impact 

Interestingly, Thirtle and Ruttan (1987, fh. 97) note that hybrid com was not invented in Iowa but in Connecticut. The supply side factor was therefore independent from the location of invention of the innovation. 

However, Griliches (1957) admits that a market may be entered because it is a springboard to other areas rather than on its own ground and suggests that the market potential , including the adjunct markets, should have been taken as an indicator for profitability of market entry. 

PERCENT OF TOTAL CORNACREAGE PLANTED WITH HYBRID SEED 

The model is based on private information dissemination and therefore limited to adoption processes in which private information is the decisive determinant. A second spatial diffusion model is based on the physical infrastructure that is complementary to innovations. Infrastructure and diffusion agencies such as distribution networks are suggested to facilitate the diffusion of innovations (McIntyre 1988). When infrastructure is an important complement it can also be an important factor for international diffusion (section 3.2.2). Formal spatial diffusion models incorporating local externalities have been reviewed in section 2.4.3. As has been noted there already, the problem of a spatial model is its simplification that the diffusion of innovation is modelled only as a spatial process. The assumption of information dissemination seems not to be as relevant for the international diffusion process as for the within-country diffusion because of international differences in national preferences and other environmental contexts. 

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