This thesis is a collection of three independent essays in applied microeconomic theory. The first chapter, co-authored with Milena Almagro, explores the conditions under which a state promotes a shared national identity on its territory. A forward-looking government that internalizes identity dynamics shapes them by implementing nation-building policies. Assimilation attempts are constrained by political unrest, electoral competition, and the intergenerational transmission of identities. We find the long-run evolution of identities to be highly sensitive to initial conditions and to temporary shocks that affect the relative political power of the ethnic groups. Interestingly, when the conditions to promote the national identity are not present, the central government avoids long-run conflict by allowing regional identities to thrive. The results point to different nation-building behavior between autocracies and democracies, with the latter being more likely to preserve regional identities. The second chapter, co-authored with Natalia Fabra, analyzes how firms' incentives to operate and invest in energy storage depend on the market structure. For this purpose, we characterize equilibrium market outcomes allowing for market power in storage and/or production, as well as for vertical integration between storage and production. Market power reduces efficiency through two channels: it induces an inefficient use of the storage facilities, and it distorts investment incentives. We illustrate our theoretical results by simulating the Spanish wholesale electricity market. The results are key to understanding how to regulate energy storage, an issue which is critical for the deployment of renewables. The third chapter explores the difficulties that endogenous preferences pose for normative work, using environmental policy design as a motivating example. I first assess how the major positions in welfare economics can be adapted to contexts in which policies shape preference formation. The implications for policy design of using different welfare criteria are then illustrated with a simple model of carbon pricing. An empirically implementable method is proposed to micro-found the relative weights that a standard welfarist approach could give to pre-policy and post-policy preferences.