Essays in financial and applied microeconomics

This thesis contains three distinct papers related to the behavior of investors or firms acting under imperfect competition. First, we consider a Kyle's (1985) model where investors can produce either a (fundamental) signal on the value of the risky asset, or a (non-fundamental) signal on the forthcoming demand from noise traders. We show that reducing the cost of the non-fundamental signal worsens price informativeness as well as the welfare of noise traders under some conditions. Then, we extend the model by allowing  nonfundamental traders to submit limit orders. Their activity is then analogous to front running. By this mean, we enrich our results and show that the potentially detrimental effect of non-fundamental information still pertains. Then, we consider a market à la Kyle (1985) where uninformed hedgers trade for risk sharing purposes with investors located on a network, who share their signal with their contacts. This hypothesis formalizes a better diffusion of information. We evaluate its effect on speculative gains and hedgers' expected utility which depends on the risk sharing role of the market. We show that the introduction of the network might simultaneously improve these two welfare measures as well as price informativeness. An original result that cannot be obtained otherwise. Finally, we consider a contribution game between two competitors of different sizes. We obtain the value of their (irreversible) contributions during each period of the game. We show that the asymmetry between the two firms strongly slowers the collaboration process, highlighting the importance of contractual arrangements in some circumstances. Also, we obtain that increasing competition might be detrimental to social welfare, because it harms the ability of the two firms to set up a mutually beneficial process of collaboration.