Portfolio optimization under dynamic risk constraints

We consider an investor faced with the classical portfolio problem of optimal investment in a log- Brownian stock and a fixed-interest bond, but constrained to choose portfolio and consumption strategies which reduce a dynamic shortfall risk measure. For continuous and discrete-time financial markets we investigate the loss in expected utility of intermediate consumption and terminal wealth caused by imposing a dynamic risk constraint. We derive the dynamic programming equations for the resulting stochastic optimal control problems and solve them numerically. Our numerical results indicate that the loss of portfolio performance is quite small while the risk is reduced considerably. We also investigate discretization effects and the loss in performance if trading is possible at discrete time points only.