Why Hold Expensive Slow-Growing Stocks?

Key Takeaways

  • Because traditional style indices are based on the completeness principle, with all stocks defined as growth, value, or both, funds based on these indices hold stocks that are neither growth nor value.

  • As a result, investors in style funds can be forced to hold expensive slow-growing stocks that have historically underperformed.

  • We propose studier framework that forms value portfolios based solely on cheap stock prices and growth portfolios based solely on fast-growing companies, seeking to eliminate the underperforming expensive slow-growing stocks.

  • This framework allows for a simple, practical implementation by forming portfolios that combine the market’s cheapest stocks with its fastest-growing stocks.

  • Our analysis shows that portfolio concentration and style timing can provide a further boost to performance.

For decades, investors have bought value and growth funds that track their respective style indices. By design, index providers construct these style indices by partitioning the full market, and the resulting value and growth indices hold stocks that are neither value nor growth. This approach to index construction often requires investors in style funds to own expensive stocks of slow-growing companies that have historically underperformed.

To remedy this problem, we propose an alternative framework that removes the expensive slow-growth stocks. Using this new blueprint, we build value and growth portfolios designed to outperform the market when combined. In addition, forming more concentrated portfolios and using style timing can deliver even better performance.

What’s Inside Your Style Index Fund?

Today’s style-based index funds track benchmark indices built with the “completeness principle,” according to which all stocks are categorized as value, growth, or some combination of both. But that’s just not true; some stocks are neither.

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The impact of “style investing” was formally examined in the academic literature by Barberis and Shleifer (2003), who showed that investor categorization by style and the flows it induces can cause asset prices within a style to move together and deviate from fundamentals. Since then, style investing has grown to become an enormous portion of the stock market. The massive scale means getting it right is important. Roughly, $14 trillion (23% of the $62 trillion U.S. stock market) passively tracks or is benchmarked to traditional style indices (see Appendix A).

A central feature of today’s dominant style index structure is the “completeness property,” the rule that an equal mix of value and growth indices must replicate the parent cap-weighted index at each annual reconstitution. The symmetry imposed by this design ensures that investing equally in both style indices is functionally equivalent to investing in the full market, eliminating any aggregate style bias. Russell, S&P, and MSCI all build their standard style indices by splitting the weight of “crossover” stocks into both their value and growth indices.1 Choice of characteristics to define style and methods for defining crossover stocks differ, but all three include stocks that are neither value nor growth.

The world’s largest asset managers create and sell style index funds, which hold much of the market’s expensively priced stocks of companies with slow or negative growth. In turn, investment advisors and consultants recommend value and growth index funds to their clients. Investors in style index funds may assume they get diversification of style. But do they? This isn’t diversification; it’s diworsification.

We ask a simple question: Why include expensive stocks of slow-growing companies in either index? We think doing so is illogical, unnecessary, and costly.

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