Risk Measurement from Theory to Practice: Is Your Risk Metric Coherent and Empirically Justified?

Abstract

I present desirable features for a risk metric, incorporating the coherent risk framework and empirical features of markets. I argue that a desirable risk metric is one that is coherent and focused on measuring tail losses, which significantly affect investment performance. I evaluate 5 risk metrics: volatility, semi-standard deviation, downside deviation, Value at Risk (VaR) and Conditional Value at Risk (CVaR). I demonstrate that CVaR is the only coherent risk metric explicitly focused on measuring tail losses, which are an important, empirical feature of markets. CVaR is the most practically useful risk metric for an investor interested in minimizing declines in the value of a portfolio at stress points while maximizing returns. Through several examples, I demonstrate that the choice of a risk metric may lead to very different portfolios and investment performance due to differences in investment selection, portfolio construction and risk management. I also demonstrate that the focus on tail losses as opposed to volatility results in superior performance - much smaller declines in value at stress points with improvements in average and cumulative returns; similar results can be achieved with other risk metrics, which are not designed to measure tail losses like CVaR Based on empirical data, practical recommendations for investment analysis, portfolio construction and risk management are included throughout the article.

Keywords: Risk Measurement, Risk Management, Investment Analysis, Investment Strategy, Asset Allocation, Portfolio Management, Portfolio Optimization

JEL Classification: G10, G11