A theoretical and practical perspective on the equity risk premium

In historical perspective, equity returns have been higher than interest rates but have also varied a good deal more. However, the average excess return has been larger than what could be expected based on classical equilibrium theory: the equity risk premium (ERP) puzzle. This paper has two objectives. First, the paper presents a comprehensive overview of the vast literature developed aimed at adjusting theory and testing the robustness of the puzzle. Here we will show that the failure of theory to link asset prices to economics is mostly quantitative by nature and not qualitative (anymore). Second, beyond providing a survey of theory, we aim for a relevant practical angle as well. Our main contribution is that we spend time on why returns have been higher than investors reasonably could have expected. We present evidence that forecasts of equity returns can be enhanced by valuation models: low valuation levels (low price-to-earnings ratios) portend high subsequent returns. While conventional wisdom (several years ago) was to use historical returns to forecast future returns, a growing consensus now recognizes that the predictive power of valuation ratios is preferred. Finally we provide some practical implications based on this predictability. While the ERP is essentially a long-term issue, the likelihood of a lower risk premium increases risk for many and means that short-term volatility might not be neglected.