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Market-cap-weighted funds give larger companies more influence; equal-weighted funds aim to give every company in the index the same weight at scheduled rebalances. Neither approach is automatically better: the choice changes your exposure to the largest and smaller companies, how often the portfolio is reset, and potentially its costs and taxes.
How the two weighting methods work
Market-cap weighting
A market-cap-weighted index assigns each company a weight in proportion to its market capitalization. Many equity indexes use a float adjustment, which excludes shares not readily available for public trading. As a result, the largest eligible companies carry the most influence on the index’s returns. S&P Dow Jones Indices explains market-cap, float-adjusted market-cap, and equal weighting.
Equal weighting
An equal-weighted index targets the same weight for each constituent, regardless of company size. That lowers the largest companies’ relative influence and raises the relative influence of smaller constituents within the same index universe. This describes a change in exposure; it does not promise lower overall risk or higher returns.
What the S&P 500 example shows
The S&P 500 Equal Weight Index contains the same companies as the capitalization-weighted S&P 500, but targets 0.2% per company at each quarterly rebalance, according to S&P Dow Jones Indices’ index page. The 0.2% target applies to this index at its rebalance, not to every equal-weight index.
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The difference is not which companies are included in this example, but how much influence each has. A cap-weighted S&P 500 gives greater weight to the biggest companies; the equal-weight version spreads weight evenly across the 500 constituents at its quarterly reset.
Why rebalancing changes the portfolio
After an equal-weight index is reset, share prices move at different rates, so the weights drift away from equal. At the next scheduled rebalance, the index resets them toward their targets. For the S&P 500 Equal Weight Index, that schedule is quarterly. S&P’s index mathematics methodology describes how price moves affect weights.
A capitalization-weighted index generally does not need to reset weights solely because prices change: companies’ relative market values change the weights naturally. Index maintenance still occurs for matters such as share-count and corporate changes. Rebalancing can mean more trading in an equal-weight strategy, but the actual turnover and its effects depend on the fund and index rules; check the fund’s published materials rather than assuming a particular figure.
Compare the fund, not just the index label
An index is a set of rules, not an investment an individual can buy directly. Investors use funds that seek to track indexes, and fund-level expenses and implementation can affect results. Compare the specific products on these points:
- Index universe and rules: Confirm which securities are eligible, how constituents are selected, and whether the two funds track indexes with the same holdings. Equal weighting does not by itself mean the underlying companies are identical.
- Company-size exposure: Look at how much influence the largest holdings have and how the fund distributes exposure among smaller constituents. Equal weighting reduces the largest companies’ relative influence within a shared universe, but does not remove market risk.
- Rebalancing and turnover: Check the index schedule and the fund’s reported turnover. A scheduled reset is a feature of the index methodology; fund trading and turnover can vary.
- Costs and tracking: Compare the current expense ratio, any brokerage costs, and tracking difference—the gap between fund performance and its benchmark. A benchmark’s results are not the same as an investor’s fund returns after expenses.
- Taxes: Consider the account type and your jurisdiction. Tax treatment depends on local rules and circumstances; a rebalance in an index does not, by itself, determine the tax outcome for an investor.
Fund example: Invesco S&P 500 Equal Weight ETF
Invesco says its S&P 500 Equal Weight ETF (RSP) seeks to track the S&P 500 Equal Weight Index, rebalances quarterly, and has a 0.20% total expense ratio on its product page. That is the issuer’s stated figure, accessed in 2026, and fund expenses can change; verify the current prospectus and product information before investing. See Invesco’s RSP product page. RSP is one implementation example, not a recommendation or the only equal-weight fund.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Can you say which one performs better?
There is no universal winner established by the weighting rule alone. A meaningful historical comparison must name the exact indexes or funds, use the same dates and a comparable total-return basis, state whether returns are before or after fees, and identify the end date. Past results do not establish which approach will perform better next.
S&P Dow Jones Indices cautions that history before an index’s launch may be hypothetical back-tested rather than live performance. Such results have limitations, including hindsight and possible survivorship or look-ahead bias; past performance is not a guarantee of future results. S&P’s equal-weight index family page provides its performance caveats.
Quick Recap
A practical decision checklist
- Decide whether you want company weights to reflect relative market size or to be reset toward equal weights.
- Check that the funds you are comparing track the same—or meaningfully comparable—constituent universe.
- Review the largest holdings and the resulting exposure to smaller constituents.
- Compare rebalance schedules, fund turnover, expense ratios, brokerage costs, and tracking difference using current fund disclosures.
- Assess tax implications for your account and jurisdiction, and compare performance only on a like-for-like basis.
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