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Why has the equal weight portfolio underperformed and what can we do about it?

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  • B. H. Taljaard
  • E. Maré

Abstract

It is widely noted that market capitalisation weighted portfolios are inefficient and underperform an equal weighted portfolio over the long-term. However, at least since 2016, an equal weighted portfolio of stocks in the S&P500 has significantly underperformed the market capitalisation weighted portfolio. In this paper, we analyse this underperformance using stochastic portfolio theory. We show that the equal weighted portfolio does appear to outperform the market capitalisation weighted portfolio over the long-term but with periods of significant short-term underperformance. In addition, we find that concentration in the market capitalisation weighted portfolio has increased in recent years and has contributed to the recent underperformance together with a significantly lower level of diversification benefits. Furthermore, we highlight an approach to improve the performance of a portfolio by dynamically selecting a market cap or an equal weighting using a rudimentary linear regression model.

Suggested Citation

  • B. H. Taljaard & E. Maré, 2021. "Why has the equal weight portfolio underperformed and what can we do about it?," Quantitative Finance, Taylor & Francis Journals, vol. 21(11), pages 1855-1868, November.
    • Handle: RePEc:taf:quantf:v:21:y:2021:i:11:p:1855-1868
    DOI: 10.1080/14697688.2021.1889020
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    Citations

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    Cited by:

    1. Migliavacca, Milena & Goodell, John W. & Paltrinieri, Andrea, 2023. "A bibliometric review of portfolio diversification literature," International Review of Financial Analysis, Elsevier, vol. 90(C).
    2. Chendi Ni & Yuying Li & Peter A. Forsyth, 2023. "Neural Network Approach to Portfolio Optimization with Leverage Constraints:a Case Study on High Inflation Investment," Papers 2304.05297, arXiv.org, revised May 2023.
    3. Ngo, Vu Minh & Nguyen, Huan Huu & Van Nguyen, Phuc, 2023. "Does reinforcement learning outperform deep learning and traditional portfolio optimization models in frontier and developed financial markets?," Research in International Business and Finance, Elsevier, vol. 65(C).
    4. Amit Pandey & Anil Kumar Sharma, 2023. "Effect of Index Concentration on Index Volatility and Performance," Asia-Pacific Financial Markets, Springer;Japanese Association of Financial Economics and Engineering, vol. 30(3), pages 559-585, September.
    5. Zaimovic Azra & Arnaut-Berilo Almira & Bešlija Rijad, 2024. "International Portfolio Diversification Benefits: An Empirical Investigation of the 28 European Stock Markets During the Period 2014–2024," South East European Journal of Economics and Business, Sciendo, vol. 19(1), pages 96-112.
    6. Steven Campbell & Qien Song & Ting-Kam Leonard Wong, 2024. "Macroscopic properties of equity markets: stylized facts and portfolio performance," Papers 2409.10859, arXiv.org, revised Oct 2024.

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