Innovation processes, interactions and diffusion in the economy.

Summary The purpose of this research is to analyze the process of formation of innovations, the interactions they generate, and the modalities of diffusion in the economic and social fabric. These three dimensions are intimately linked, and it is to the explicitation of the corresponding links that this work is devoted. The system of interactions includes on the one hand the agents (consumers, firms and public decision-makers) and on the other hand the grouping of these agents on an aggregate scale (industries, consumer associations, political groups, institutions). Interactions can have positive aspects. For example, they can improve the diffusion of information about the characteristics of a new product between informed and uninformed consumers. They can also have negative effects, such as the increase in knowledge required to participate in the productive system, knowledge and mastery that characterize what we often designate under the general term of complexity. In the first part, we study the link between complexity and innovation on an aggregate scale. In the second part, we first review the different methodologies that allow us to test and measure the importance of interactions on innovation formation. We then show that innovative firms weave an information network among themselves. The linear model of innovation where ideas and discoveries are transformed into development projects and then into technological innovations seems to correspond less and less to reality. Finally, in the last part, we determine the role of local interactions on the diffusion of innovation. We adopt a microeconomic analysis framework and propose an overview of the main statistical and economic models of information diffusion concerning the characteristics of a new technology in a social network. We then propose a model in which we specify a local communication network, assuming that only socially close agents can communicate information among themselves through a "word of mouth" mechanism. We study in this context the diffusion of a new technology by a firm producing a good of superior quality.