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Short answer: The Nasdaq-100 is a concentrated large-company index of Nasdaq-listed, non-financial businesses, with a much larger technology and consumer-discretionary presence. The S&P 500 is a broader U.S. large-cap benchmark that includes financial companies and spreads exposure across more sectors. Both are market-cap-oriented, but the Nasdaq-100 uses modified market-cap weighting while the S&P 500 uses float-adjusted market-cap weighting.
In Nasdaq Global Indexes’ comparison for December 31, 2007 through March 31, 2026, the Nasdaq-100 had the higher annualized return and the higher annualized volatility. That history describes what happened in one measured period; it is not a forecast and does not make either index automatically suitable for every portfolio.
The core differences at a glance
The names can sound interchangeable because both indexes contain many very large U.S. companies. Their rules produce different portfolios, however. The Nasdaq-100 starts with the largest eligible companies listed on Nasdaq and removes financial companies. The S&P 500 is designed to represent the large-cap segment of the U.S. equity market across sectors.
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A free scan shows the junk files, broken settings and background clutter dragging Windows down - then fixes them in one click.Free scan · Windows 10 & 11| Feature | Nasdaq-100 | S&P 500 |
|---|---|---|
| What it represents | Large Nasdaq-listed, non-financial companies | Large-cap U.S. equities across economic sectors |
| Number of index constituents | 100 eligible companies | 503 constituents shown by S&P Dow Jones Indices on August 31, 2026; the number of securities can differ from the number of constituent companies |
| Financial companies | Excluded by eligibility rules | Included |
| Weighting approach | Modified market-cap weighting | Float-adjusted market-cap weighting |
| Technology weight in the cited sector snapshot | 59.8% on March 31, 2026, using ICB classifications | 39.1% on March 31, 2026, using ICB classifications |
| Consumer-discretionary weight in the cited sector snapshot | 21.2% on March 31, 2026 | 13.8% on March 31, 2026 |
| Financials weight in the cited sector snapshot | 0.0% on March 31, 2026 | 10.2% on March 31, 2026 |
| Largest S&P 500 constituent | Not a like-for-like figure in the cited material | 8.1% on August 31, 2026 |
| S&P 500 top-10 weight | Not a like-for-like figure in the cited material | 37.8% on August 31, 2026 |
The dates matter. Sector figures come from a March 31, 2026 comparison, while the S&P 500 concentration figures come from an August 31, 2026 snapshot. Weights change with prices, index reviews and corporate actions, so they should not be treated as permanent characteristics.
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What the Nasdaq-100 holds
Eligibility is based on listing, size and industry
Nasdaq defines the Nasdaq-100 as the 100 largest companies listed on its exchange that meet the index’s non-financial eligibility requirement. The rule makes the index a market slice rather than a complete representation of all Nasdaq-listed stocks. A company can be large and well known yet remain outside the index if it does not satisfy the listing, industry or other methodology conditions.
The Nasdaq-100 is also not the Nasdaq Composite. The Composite covers a much wider set of Nasdaq-listed securities, while the Nasdaq-100 is a selected large-company index. Statements about the Composite’s breadth or performance should not be substituted for statements about the Nasdaq-100.
Methodology changed in 2026
Nasdaq announced methodology changes on March 30, 2026 and explained that the revisions took effect on May 1, 2026. That timing matters when comparing an older description with a current one: eligibility, constituent entry and weighting details should be read from the post-May 1 methodology rather than assumed from an earlier article. The broad identity remains the same—large Nasdaq-listed companies outside the financial sector—but the operational rules are time-sensitive.
What the S&P 500 holds
A broad large-cap U.S. benchmark
S&P Dow Jones Indices describes the S&P 500 as a measure of the large-cap segment of the U.S. equity market. Its selection framework spans sectors, so financial companies, industrial businesses, health-care companies, communication-services firms, consumer companies and other industries can all be represented.
The index page displayed 503 constituents on August 31, 2026. That does not mean there were 503 separate operating companies in every sense: an index can contain multiple share lines or other securities associated with one company. For portfolio analysis, distinguish the number of index securities from the number of corporate issuers.
Why the S&P 500 is not an equal slice of 500 companies
The S&P 500 uses float-adjusted market-cap weighting. Companies with a larger value of publicly available shares receive larger weights, while shares not considered freely available to public investors are adjusted out of the calculation. As a result, the index’s biggest companies can have a substantial effect on its return even though the index contains hundreds of constituents.
How the weighting systems change your exposure
Nasdaq-100: modified market-cap weighting
The Nasdaq-100 is market-cap oriented, but its methodology is described as modified market-cap weighting rather than an unadjusted market-cap formula. The modification is implemented through Nasdaq’s index rules and can affect how much any one eligible company contributes. The exact limits, review dates and treatment of corporate events belong to the current methodology effective from May 1, 2026.
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For an investor, the practical point is that the largest eligible companies generally matter most, while the method can prevent the portfolio from being a simple dollar-for-dollar mirror of total market value. This produces a concentrated large-company growth profile without making every constituent an equal holding.
S&P 500: float-adjusted market-cap weighting
The S&P 500’s float adjustment focuses the index on shares available to public investors. A company with a large public float can therefore carry more weight than a similarly sized company with less stock available for trading. Because the system is capitalization based, successful mega-cap companies can become increasingly influential as their market values rise.
What the two systems have in common
Neither index gives every constituent the same weight. Both are dominated by larger companies, and both can become more concentrated when a small group of mega-cap stocks rises faster than the rest of the market. Their different eligibility rules and weighting adjustments mean that two funds tracking the indexes can still have materially different sector and single-company exposures.
Sector exposure: the clearest source of difference
Nasdaq Global Indexes reported the following sector weights on March 31, 2026, using Industry Classification Benchmark classifications:
| Sector | Nasdaq-100 | S&P 500 | What the difference implies |
|---|---|---|---|
| Technology | 59.8% | 39.1% | The Nasdaq-100 is more dependent on technology-related earnings, valuations and investment cycles. |
| Consumer discretionary | 21.2% | 13.8% | The Nasdaq-100 has greater exposure to companies whose revenue can be sensitive to household demand and economic confidence. |
| Financials | 0.0% | 10.2% | The S&P 500 includes banks, insurers and other financial businesses; the Nasdaq-100 excludes financial companies by design. |
These three rows do not describe every sector, but they show why the indexes can react differently to the same news. Interest-rate expectations, technology capital spending, advertising demand, consumer spending, credit conditions and bank profitability do not affect the two portfolios in equal proportions.
Technology concentration is an exposure, not a guarantee
A higher technology weight can help when technology earnings and valuations lead the market. It can hurt when the sector faces falling demand, tighter financial conditions, regulatory pressure or a change in investor preferences. The index construction creates sensitivity to those forces; it does not predict the direction or size of the next move.
The S&P 500 is broader but still concentrated
Sector breadth does not eliminate concentration risk. S&P Dow Jones Indices reported that its largest constituent represented 8.1% of the index and that the ten largest constituents represented 37.8% on August 31, 2026. Those figures show that a broad constituent count can coexist with substantial influence from a relatively small group of companies.
Do not compare those percentages directly with a Nasdaq-100 top-ten figure unless both are calculated for the same date, with the same constituent definitions and the same treatment of share classes. The cited Nasdaq comparison does not provide a matching Nasdaq-100 concentration snapshot.
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Historical return and risk evidence
Nasdaq Global Indexes published a comparison covering December 31, 2007 through March 31, 2026. The figures below are provider-published index results for that selected window, not a forecast and not a promise that an investable fund will match the index exactly.
| Measure for the stated period | Nasdaq-100 | S&P 500 |
|---|---|---|
| Cumulative total return | 1,258% | 531% |
| Annualized return | 15.4% | 10.6% |
| Annualized volatility | 22.9% | 20.0% |
| Correlation of daily returns | 93% | |
| Average volatility difference over the 18-year comparison | Nasdaq-100 averaged 2.9 percentage points higher annualized volatility | |
The result is a clear historical trade-off in this window: the index with the stronger annualized return also experienced greater annualized volatility. Volatility measures the dispersion of returns, not the maximum possible loss, and it does not tell you how quickly an index recovers after a decline.
The high daily-return correlation shows that the indexes often moved in the same broad direction. Correlation is not sameness, however. Different sector weights, excluded financials and different single-company weights can still produce meaningful differences in drawdowns and recoveries.
A separate trailing-period statistic
In a separate explainer, Nasdaq described approximate trailing 10-year total returns through December 31, 2025 of about 500% for the Nasdaq-100 and about 300% for the S&P 500. Those figures use a different period and presentation from the December 31, 2007–March 31, 2026 comparison, so they should not be combined with the earlier table or treated as an updated version of it.
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Is the Nasdaq-100 riskier than the S&P 500?
For the cited 2007–2026 comparison, the Nasdaq-100 had higher measured annualized volatility. Its design gives a plausible structural explanation: a larger allocation to technology and consumer discretionary companies, no financial companies, and meaningful influence from a smaller set of very large businesses. A narrower group of industries can make the index more sensitive to sector-specific news.
That does not make the S&P 500 low risk. Its float-adjusted capitalization method also allows its largest companies to dominate results, as the August 31, 2026 concentration figures illustrate. A broad sector list reduces some forms of concentration but cannot remove equity-market risk, valuation risk or the possibility that several large constituents fall together.
Risk should therefore be separated into at least four questions:
- Volatility: How widely have returns varied over the chosen period?
- Drawdown: How far did the index fall from a previous high, and how long did recovery take?
- Concentration: How much depends on the largest companies or sectors?
- Exposure risk: Which economic drivers—technology investment, consumer demand, credit or interest rates—matter most?
The published comparison directly answers the volatility question for its stated window. It does not establish a permanent ranking for every future period or answer the other three questions by itself.
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Holding exposure to both indexes can add some sector and constituent differences, but the names alone do not guarantee broad diversification. Both portfolios are built around large U.S. companies, and both can contain the same mega-cap businesses. When the same companies have large weights in both, combining the indexes may increase exposure to those companies rather than create an independent second allocation.
A precise overlap percentage should be calculated from holdings published for the same date, using the same treatment of share classes and weights. The evidence cited here does not provide a matched current overlap percentage, so no single number should be assumed.
To evaluate a proposed combination, compare the two funds’ latest holdings side by side, identify repeated companies, add their combined weights, and then examine sector totals. Also check whether one vehicle uses sampling, derivatives or other implementation methods that make its portfolio differ from the underlying index.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Which index may fit a particular portfolio role?
When a broad U.S. large-cap core is the priority
The S&P 500 is designed for investors seeking a single benchmark covering the large-cap U.S. market across sectors. Its inclusion of financials and other industries can reduce dependence on the technology and consumer-discretionary cycles that are more prominent in the Nasdaq-100. It remains an equity index with meaningful mega-cap concentration, not a complete all-company or all-asset portfolio.
When a deliberate technology and growth tilt is acceptable
The Nasdaq-100 may be used when an investor specifically wants greater exposure to large Nasdaq-listed, non-financial companies and accepts the resulting concentration. The higher historical return in the cited period came with higher historical volatility, so the tilt should be treated as an intentional risk decision rather than a free performance upgrade.
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When the goal is to complement an existing portfolio
Start with what you already own. A portfolio that already has a large U.S. technology allocation may gain less diversification from adding the Nasdaq-100 than its label suggests. Conversely, a portfolio lacking technology and consumer-discretionary exposure may change materially when the Nasdaq-100 is added. Review total look-through weights rather than evaluating each index in isolation.
A practical comparison checklist
- Set the observation date. Record the date for holdings, sector weights and concentration figures. Do not mix a March snapshot with an August snapshot and call the result current.
- Confirm the index methodology. For the Nasdaq-100, use the rules effective May 1, 2026 or any later revision. For the S&P 500, verify the current eligibility and float-adjustment rules.
- Check the actual vehicle. An index fund, exchange-traded product, option or futures contract can introduce fees, tracking differences, leverage, expiration and counterparty considerations that are not properties of the index itself.
- Compare look-through holdings. List the largest positions, repeated companies and their combined weights instead of relying on index names.
- Compare sectors on one classification basis. Sector labels and classifications can change; use the same provider, date and classification system for both indexes.
- Choose a risk measure that matches your question. Use volatility for variability, maximum drawdown for loss from a peak, and recovery time for how long a decline lasted. A single annualized figure cannot answer all three.
- Test concentration in your whole portfolio. Include individual shares, employer stock and other funds. Index diversification is only one layer of diversification.
Risks that remain after choosing an index
Market and valuation risk
Both indexes represent equities. Their values can fall when economic growth weakens, earnings disappoint, risk appetite changes or valuations contract. A favorable long-term history does not prevent losses over shorter horizons.
Methodology and reconstitution risk
Index providers periodically review constituents and rules. The Nasdaq-100’s 2026 methodology revision demonstrates that eligibility and weighting are not frozen forever. A reconstitution can change sector and company exposures even when an investor has not changed the vehicle.
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Implementation and tracking risk
A fund or derivative seeks to provide exposure to an index but may not match its published return because of fees, taxes, trading costs, cash management, sampling, corporate-action treatment or derivative mechanics. Examine the product’s own documents rather than assuming index performance is the same as investor performance.
Time-horizon risk
The historical comparison spans more than 18 years, while many investors need money sooner. A long observation window can contain several market regimes and still be unsuitable evidence for a short-term spending goal. Match the equity allocation to the date on which the money is needed.
Bottom line
The Nasdaq-100 is the more concentrated, technology-heavy choice: it selects large Nasdaq-listed non-financial companies and, in the cited historical comparison, delivered higher annualized return alongside higher annualized volatility. The S&P 500 is the broader sector benchmark, includes financials and hundreds of constituents, but its capitalization weighting still gives substantial influence to its largest companies. Choose between them by examining your existing exposures, tolerance for concentration and time horizon—not by treating past outperformance as a promise.
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