The Problem with Equal Weight Index Funds

Quick Overview

Equal-weighted index funds generally outperform market-cap-weighted funds over the long run, as shown by historical data, because they systematically tilt toward smaller and lower-priced stocks while avoiding the negative momentum associated with over-concentration in large, high-priced stocks, though they incur higher turnover and transaction costs.

Key Points: The S&P 500 Equal Weight Index has historically outperformed the S&P 500 Market Cap Weighted Index over more than two decades (00:40). Equal-weighted indices assign equal weights to all stocks, contrasting with market-cap-weighted funds which assign weights based on size (00:22). The equal-weighted approach results in a tilt toward smaller and lower-priced stocks, leading to significantly different sector exposures (01:04, 06:22). The equal-weighted index exhibits higher volatility (Standard Deviation 16.11% vs 17.19% for 15Y data) but historically better risk-adjusted returns (Historical Sharpe 0.653 vs 0.5429 for 15Y data) (04:44). A key drawback of equal weighting is higher turnover; the S&P 500 Equal Weight Index had five times the turnover of the S&P 500 market-weight index over the prior 30 years (07:21). The factor regression analysis shows the equal-weight fund loads positively on Size and Value factors and negatively on the Momentum factor (08:31). Dimensional funds use systematic tilting (like equal weighting) to target factors like Size and Value, avoiding the negative momentum exposure inherent in cap-weighted funds (10:33, 12:22).

Context: The video addresses the common investor question regarding the merits of equal-weighted index funds versus traditional market-capitalization-weighted index funds, using research papers from S&P Dow Jones Indices and Vanguard, along with factor regression analysis from Dimensional and performance data, to explain the historical performance, risk profile, and systematic factor exposures of each approach.

Detailed Analysis

Equal-weighted index funds systematically outperform market-cap-weighted indices over the long term because they inherently tilt toward smaller, cheaper stocks and avoid the momentum exposure inherent in cap-weighted funds, despite incurring higher turnover costs. Market-cap-weighted indices are passive, assigning weights based on market value, leading to high concentration in the largest companies, a situation that has become extreme recently (00:38, 02:28). Data shows the S&P 500 Equal Weight Index has outperformed the market-cap-weighted index over decades (00:41, 01:07). Risk metrics show the equal-weight fund has slightly higher volatility (Standard Deviation) but better risk-adjusted returns (Sharpe Ratio, Sortino Ratio) over 15 years (04:44). The factor regression analysis for the equal-weight ETF confirms it has positive loadings on Size and Value factors and a negative loading on Momentum, which explains its historical outperformance relative to the cap-weighted benchmark (08:31). Conversely, the Dimensional US Core Equity 1 Index, which uses a systematic approach to tilt factors, also shows these factor exposures but avoids the high momentum tilt of the equal-weight fund (12:19, 12:22). The primary trade-off for equal weighting is significantly higher turnover and associated costs, as the fund must constantly sell winners and buy losers to maintain equal weights (07:00, 07:25).