A standard index fund weights its holdings by market capitalization — Apple gets a larger share of an S&P 500 fund than smaller companies, in proportion to the dollar value of all outstanding shares. An equal-weighted alternative gives every company in the index the same weight, regardless of size. The two produce noticeably different portfolios despite tracking the same index of companies.
This page is about what each weighting actually does, the historical performance differences, and whether equal weighting is worth the extra fees and tax complexity it usually involves.
Each company's weight in the index = its market cap / total market cap of all index members.
In the S&P 500 (cap-weighted), the top 10 companies typically represent 30–35% of the entire index. The bottom 100 companies combined represent less than 5%.
This is the default for almost every major index — S&P 500, total US market, MSCI All-World, etc.
Each company's weight = 1 / number of companies. In an equal-weighted S&P 500, each of the 500 companies is 0.2% of the portfolio, regardless of size.
To maintain equal weights, equal-weighted funds rebalance frequently — selling positions that have appreciated and buying ones that have lagged. This rebalancing is the source of most of the difference between cap-weighted and equal-weighted returns.
The portfolio is dominated by the largest companies. In recent years, the top 10 names — large-cap technology and consumer companies — drove most of the returns. The portfolio is implicitly a bet on those companies continuing to perform well.
Each of the 500 companies is 0.2%. Smaller mid-caps within the index get much more weight than they would in a cap-weighted version. The portfolio is implicitly a bet on the broader middle of the index, including smaller companies.
The result is meaningful tilts:
| Factor | Cap-weighted | Equal-weighted |
|---|---|---|
| Average company size | Large | Mid-cap leaning |
| Sector concentration | High in dominant sectors | More balanced |
| Single-stock risk | Significant in largest names | Diffused |
| Style | Slight growth tilt | Slight value tilt |
| Size factor | Large | Smaller |
Equal weighting is, indirectly, a small/mid-cap and value tilt — though not as strong as buying explicit small-cap or value funds.
Equal-weighted indexes have, historically, outperformed cap-weighted versions by 1–2 percentage points annually over multi-decade periods.
This sounds compelling. Three caveats reduce the apparent advantage:
Equal-weighted ETFs typically charge 0.20% (RSP, the largest equal-weighted S&P 500 fund) vs. 0.03% for cap-weighted (VOO, IVV, etc.). The 0.17% fee difference compounds over decades.
Equal weighting requires frequent rebalancing — selling winners, buying losers — which produces capital gains distributions in taxable accounts. Cap-weighted indexes naturally hold their winners with no rebalancing.
For tax-deferred accounts (401(k), IRA), this does not matter. For taxable accounts, the tax drag can be 0.20–0.50% annually.
Most of the equal-weighted "premium" can be explained by the size and value factor exposures it implicitly has. If you wanted those factor exposures explicitly, you could get them more cleanly with explicit small-cap value funds at lower cost.
In other words, equal weighting is not a free lunch — it is a particular factor tilt with a particular cost. Whether it is the best way to access those tilts is the real question.
Expense ratios: 0.03–0.10%.
Expense ratios: 0.20%+.
For most investors, the marginal complexity of equal weighting is not worth the costs:
The equal-weighted approach is reasonable if you specifically want the implicit tilts; it is not better than cap-weighted in any general sense.