# Value matters: Predictability of Stock Index Returns

**Authors:** Natascia Angelini, Giacomo Bormetti, Stefano Marmi, Franco Nardini  
**arXiv:** [1204.5055](https://arxiv.org/abs/1204.5055)  
**Date:** 2012-04-23  
**Summary page:** https://www.summarizepaper.com/en/paper/1204.5055v2/

## Key points

- The paper introduces a dynamical model of stock index returns based on the Cyclically Adjusted Price Earning (CAPE) valuation ratio developed by Robert Shiller.
- The CAPE ratio has predictive power for long-horizon market performance.
- Stock return growth is influenced by three key components: momentum, fundamental, and driving in the discrete time dynamics framework discussed by the authors.
- For large horizons, both the expected rate of return and gross return exhibit linearity with respect to the initial logarithmic CAPE value.
- Despite potential short-term bubbles and crashes generated by the momentum component, the CAPE valuation ratio remains a reliable reference point for predicting future long-run returns.
- The variance of returns converges to zero at a rate consistent with diffusive behavior in stock prices.
- The revised version of the paper includes an econometric section introducing new insights through predictive regressions.

## Summary

The paper "Value Matters: Predictability of Stock Index Returns" by Natascia Angelini, Giacomo Bormetti, Stefano Marmi, and Franco Nardini presents a simple dynamical model of stock index returns based on the Cyclically Adjusted Price Earning (CAPE) valuation ratio developed by Robert Shiller. This ratio has shown to have predictive power for long-horizon market performance. The authors discuss a discrete time dynamics framework where stock return growth is influenced by three key components: momentum, fundamental, and driving. Through their analysis, they demonstrate that for large horizons, both the expected rate of return and gross return exhibit linearity with respect to the initial logarithmic CAPE value. They also show that the variance of these returns converges to zero at a rate consistent with diffusive behavior in stock prices. Despite potential short-term bubbles and crashes generated by the momentum component, the CAPE valuation ratio remains a reliable reference point for predicting future long-run returns. The revised version of the paper includes an econometric section introducing new insights through predictive regressions. With 27 pages, 3 figures, and 2 tables included in this study, readers can gain valuable knowledge about how value considerations impact the predictability of stock index returns in financial markets.