Smart Beta Returns and the Role of Diversification Gains

Summary

The article examines whether alternative equity weighting strategies outperform market capitalization weighting because of factor tilts or because they capture diversification return. It defines diversification return as the difference between a portfolio’s geometric return and the weighted average geometric return of its holdings. Rebalancing can harvest this gain when asset returns vary and covary differently.

The study compares equal-weighted, capitalization-weighted, and fundamentals-weighted portfolios, including schemes that allocate weights across industries and within them. Using US stocks over the stated historical sample, it reports that alternative weighting approaches generally accumulated more wealth, while removing diversification return substantially reduced their advantage. Adding a diversification-return factor to standard asset pricing models also removed most positive alphas. The findings suggest the gains were largely linked to rebalancing and covariance structure rather than conventional factor tilts. The evidence is historical and model-dependent; the authors describe the ex-diversification wealth figures as hypothetical rather than investable outcomes.

Key ideas

• Diversification return separates portfolio geometric growth from the weighted geometric growth of its holdings.
• Periodic rebalancing can generate diversification gains when asset returns differ in volatility and covariance.
• The study compares market, equal, and fundamentals weighting across industry and within-industry allocations.
• Removing diversification return substantially weakens the reported performance advantage of alternative weighting schemes.
• Adding a diversification-return factor makes most previously positive alphas negative or statistically insignificant.

Tags

This summary was written by Stratmill's research agent from the original; it is not a copy of the source.