April, 2024
Most investors commonly believe that the familiar S&P 500 index comprises the largest 500 US stocks by market capitalization. That’s not true. In fact, Standard & Poors has a long list of eligibility requirements developed for its committee’s use that automatically excludes many big U.S. companies not meeting their particular criteria. As of last February, 73 companies ranking among the largest 500 in the U.S. by market capitalization that were included in competitors’ market cap-weighted indexes were excluded from the S&P 500 index. The combined group represents $2.1 trillion in market value. That is 25% more than Australia’s entire stock market valuation.1
For example, to be included in the S&P index, companies must have positive earnings over the past four quarters. Further S&P index weighting does not necessarily correspond to market weight — usually due to anticipated trading issues, particularly for less traded stocks. Accordingly, many index lists created by S&P and others frequently use stock representations of market exposure for fund managers. Therefore, as with our S&P example, a firm’s index rules may cloud investors’ understanding of what their portfolio holds and thus the expected return to anticipate.2
Exhibit 1: Largest U.S. Companies Excluded from S&P 500 Index
Comparison of US-listed securities by market cap as of February 29, 2024
Source: Dimensional Fund Advisors using data from Russell, S&P, and MSCI.
Companies not in the S&P 500 Index are in the top 500 stocks by market capitalization in the Russell 3000 Index as of February 29, 2024, but absent from the S&P 500 Index. The Russell 3000 index is market cap weighted.
Frank Russell Company is the source and owner of the trademarks, service marks, and copyrights related to the Russell Indexes. © 2024 S&P Dow Jones Indices LLC, a division of S&P Global. MSCI data © MSCI 2024.
Indices are not available for direct investment. This information is intended for educational purposes and should not be considered a recommendation to buy or sell a particular security.
Do Small Cap Indexes Only Have “Small” Stocks?
Small cap stock indexes funds all have a serious index inconsistency. For instance, the name of the Russell 2000 Index might make you believe it holds stocks only smaller than the 1,000th largest US stock by market cap weighting. That is true only at the beginning of each annual reconstitution.
Russell’s index construction protocols cater to fund managers dealing with tracking an index of costly-to-trade small stocks — a cost compounded if it must be done too often. Other index providers buy or sell the very same stocks, all traded at the same times. Similar to the S&P 500, Russell actively incorporates methodological simplifications, such as bands minimizing turnover near market capitalization breakpoints and multi-week lags between the security rank date and reconstitution date. Again, the market is represented, but not replicated. We note those adjustment reduced the Russell 2000’s turnover from 29.8% on average, from 1996–2005, to 11.8% since 2006.
While Russell modifications reduce the negative market impact of selling or buying small stocks too often as they approximate the small market index, they come at the expense of reduced expected returns due to style drift as stocks grow in size. Funds licensing the Russell 2000 Index, for example, on average had more than 20% of its constituent weight within the largest 1,000 stocks. Implementing a small stock strategy whose portfolio protocols are guided by prioritizing dimensional drivers of returns from financial science, rather than simply conform to arbitrary tracking targets, better position portfolios to realize the enhanced expectations of small stock returns.
Exhibit 2: Bending Index Rules
Weighting over time of the larger 1,000 stocks in the Russell 2000 Index, December 2009 to August 2023
Source: Source: Dimensional Fund Advisors using data from Russell. Frank Russell Company is the source and owner of the trademarks, service marks, and copyrights related to the Russell Indexes.
Trusting the Market for Returns, Not Tracking
Conventional indexing tracks the market (at least to a certain extent) to keep costs lower. The problem is that hedge funds know that index providers tell index managers what to hold and when to trade and ruthlessly exploit an opportunity. Consequently, the limited flexibility of index rebalancing leads to degraded outcomes. Long periods between index reconstitutions to minimize opportunistic trading causes considerable style drift — too many small stocks moving out of index alignment, creating more opportunity costs from degraded expected returns due to reduction of size exposure.
Dimensional Fund Advisors, employing a management process refined over decades, systematically focuses on portfolio segments, and flexibly chooses from a group of similar securities with higher return characteristics. Drawing insights from financial science, information derived from prices screens securities in real time with higher expected returns. Further value through incremental daily trading without unreliable guesswork of active management, allows for implementation opportunities.
FOOTNOTES
1. Australian stocks in the MSCI All Country World IMI index. MSCI data @MSCI 2024
2. How many readers actually study stock index fund prospectus and compare market-weighted lists?