This dissertation studies the effects of economic policies on investment, growth and welfare. The first chapter examines the welfare implications of bank capital requirements in a general equilibrium model in which a dynamic banking sector endogenously determines aggregate growth. Due to government bailouts, banks engage in risk-shifting, thereby depressing investment efficiency; furthermore, they over-lever, causing fragility in the financial sector. Capital regulation can address these distortions and has a first-order effect on both growth and welfare. In the model, the optimal level of minimum Tier 1 capital requirement is 8%, greater than that prescribed by both Basel II and III. Increasing bank capital requirements can produce welfare gains greater than 1% of lifetime consumption. The second chapter studies fiscal policy design in an economy in which endogenous growth risk and asset prices are a first-order concern. When (i) the representative household has recursive preferences, and (ii) growth is endogenously sustained through R&D investment, fiscal policy alters both the composition of intertemporal consumption risk and the incentives to innovate. Tax policies aimed at short-run stabilization may substantially increase long run tax and growth risks and reduce both average growth and welfare. In contrast, policies oriented toward asset price stabilization increase growth, wealth and welfare by lowering the slope of the term structure of equity yields.