Description: This article examines how parameter uncertainty leads to uncertainty in Value at Risk VaR estimates. Lacking a closed form solution, we use a first order approximation of VaR to map parameter changes into changes in the VaR value. When the asymptotic distribution of parameter estimates is normal, this implies a normal approximation of the confidence interval about VaR. We describe this approximation in detail and explore some extensions to risk factor modeling.

Description: Much of the push for ERM has come from regulators and rating agencies, but it is being applied in internal company decision-making as well. This paper reviews the progress made and the needs still outstanding in two key areas of application: optimal capital level for an insurer and risk-adjusted profitability of business units. The basic conclusion is that progress has been made in these areas, but more is needed. Building models is not emphasized—it will be assumed that a state-of-the art model is available. The emphasis is on using such models in decision-making.