Risk Premia Forecasts: Modest Dip In September

 | Oct 06, 2014 06:33AM ET

The expected risk premium for the Global Market Index (GMI) dipped moderately in September vs. the previous month. GMI, an unmanaged, market-value weighted mix of the last month’s 4.7% estimate.

Adjusting for short-term momentum and longer-term mean-reversion factors (defined below) further reduces the current ex ante risk premium to 4.0% for GMI vs. the adjusted 4.2% prediction for last month’s estimate.

The current projections are quite low in comparison with the actual results in recent history. GMI’s realized risk premium is substantially higher vs. today’s forecast: 11.0% for the trailing three-year period through September 2014.

Here’s a summary of the current risk premia projections for GMI and the major asset classes:

For additional perspective on recent history, here’s a recap of rolling three-year annualized risk premia for GMI, US stocks (Russell 3000) and US Bonds (Barclays Aggregate Bond Index) for the last ten years:

Finally, here’s a brief summary of the methodology and rationale for the estimates above. The basic idea here is to reverse engineer expected return based on assumptions about risk. Rather than trying to predict returns directly, this approach relies on the somewhat more reliable model of using risk metrics to estimate performance of asset classes. The process is relatively robust in the sense that forecasting risk is slightly easier than projecting return. With the necessary data in hand, we can estimate the implied risk premia using the following inputs:

1) an estimate of GMI’s expected market price of risk, defined here as the Sharpe ratio, which is the ratio of risk premia to volatility (standard deviation).

2) the expected volatility (standard deviation) of each asset

3) the expected correlation for each asset with the overall portfolio (GMI)

The estimates above are drawn from the historical record since 1998 and are presented as a first approximation for modeling the future. The projected premium for each asset class is calculated as the product of the three inputs above. GMI’s ex ante risk premia is computed as the market-value-weighted sum of the individual projections for the asset classes.

The framework for estimating equilibrium returns was initially outlined in a Modern Investment Management: An Equilibrium Approach