Increases CAPE Ratio Predictability with a Simple Adjustment

Key Takeaways

• Aligning price and earnings by firm boosts CAPE accuracy
• Market‑cap weighting outperforms earnings‑weighted traditional CAPE
• Out‑of‑sample R² rises to 0.575 for ten‑year returns
• Predictive gains strongest in recent decades despite criticism
• Dynamic allocation using Component CAPE improves certainty‑equivalent returns

Summary

A new working paper demonstrates that a simple adjustment to the cyclically adjusted price‑earnings (CAPE) ratio—aligning index constituents and applying market‑cap weights—significantly sharpens its ability to forecast ten‑year equity returns. The revised Component CAPE delivers an out‑of‑sample R² of 0.575, well above the 0.467 of the traditional aggregate measure, and the gain is especially pronounced in the most recent decades. The authors also show that the metric adds economic value in dynamic asset‑allocation tests, producing higher certainty‑equivalent returns than static 60/40 or historical‑mean benchmarks. Advisors are urged to adopt the adjusted CAPE for strategic, long‑horizon allocation decisions.

Pulse Analysis

The cyclically adjusted price‑earnings ratio has been a staple for estimating long‑term market expectations, yet critics have argued that its predictive power has eroded as the S&P 500’s composition evolved. Traditional CAPE mixes today’s index prices with historical earnings drawn from firms that may no longer be constituents, creating a mismatch that dilutes the signal. By realigning the numerator and denominator to the same set of companies, the new Component CAPE corrects this measurement error, offering a cleaner view of valuation trends.

The research team constructs the Component CAPE by weighting individual firm‑level CAPEs with their market capitalizations, mirroring how capital is actually allocated in the market. In a constant‑slope out‑of‑sample framework, this approach yields an R² of 0.575 for ten‑year return forecasts—significantly higher than the 0.467 achieved by the conventional aggregate method. The improvement holds up under bootstrap inference, Bonferroni adjustments, and false‑discovery‑rate controls, confirming its statistical robustness. Notably, the advantage intensifies in the post‑2000 era, directly challenging the claim that CAPE has lost relevance.

For practitioners, the implications are immediate. A market‑cap‑weighted, component‑aligned CAPE provides a more reliable input for strategic asset allocation, enhancing certainty‑equivalent returns when embedded in dynamic allocation models. Advisors should integrate this refined metric alongside macro‑economic, trend, and risk signals rather than treating it as a standalone timing tool. By doing so, they can offer clients a disciplined, evidence‑based framework for setting long‑horizon expectations and optimizing portfolio risk‑return profiles.