Industrial investments, competition and diversification of the food offer.

Summary The aim of this thesis is to study the possibility and economic feasibility of product diversification and improvement of food quality characteristics by companies, in a context in which these modifications are subject to technical constraints that induce non-negligible costs, not necessarily valued by the market. In this context, we seek to understand to what extent it is possible for public authorities to intervene to encourage firms to make sufficient efforts (in terms of upstream investment) to promote the marketing of products that conform to the quality desired by society. We have applied these research perspectives to two important and topical societal issues, namely the coexistence of GMO and non-GMO sectors and the question of health and nutrition through the issue of the entry of more acceptable product ranges from a nutritional point of view (less sugar, less fat, etc.). These issues, which occupy the two parts of the thesis, are elaborated by mobilizing tools of the Theory of Industrial Organization. The results show that spontaneous choices of product lines by firms are not always socially satisfactory, which implies public intervention under certain conditions. In the case of GMO/non-GMO coexistence, the non-GMO product may not have the desired characteristic in the absence of regulation. In the case of nutritional issues, the firms present on the market do not systematically offer foods that are favorable from a health point of view in the absence of public intervention. The general conclusion of the thesis is that it is often necessary to combine several public instruments. In the case of GMO/non-GMO coexistence, public authorities can effectively manage coexistence by simultaneously acting on the labeling threshold, the conditions for testing and control, and the level of the penalty. In the case of the nutritional issue, intervention through an R&D subsidy has certain weaknesses, such as the risk of the subsidy being used by the firm or inducing distortions to the detriment of public health. This suggests combining the R&D subsidy with another instrument such as taxation.