Short answer: The Nasdaq-100 is a concentrated basket of the 100 largest non-financial companies listed on Nasdaq, while the S&P 500 is a broad U.S. large-cap benchmark spanning many sectors, including financials. Both are market-cap-oriented, but the Nasdaq-100 uses modified market-cap weighting and the S&P 500 uses float-adjusted market-cap weighting. In Nasdaq Global Indexes’ comparison from December 31, 2007, through March 31, 2026, the Nasdaq-100 produced the higher annualized return (15.4% versus 10.6%) and higher annualized volatility (22.9% versus 20.0%). That historical advantage came with greater concentration and should not be treated as a forecast.
What each index represents
Nasdaq-100
The Nasdaq-100 consists of 100 of the largest companies listed on Nasdaq that are not classified as financial companies. Its eligibility rules make it a distinctive slice of the U.S. and international corporate market: a company must be listed on Nasdaq, be large enough for inclusion, and fall outside the financial sector under the index methodology.
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The index is often used as a shorthand for large technology companies, but that description is incomplete. It also includes companies in consumer discretionary, health care, communications and other industries. Technology is its dominant exposure because many of the world’s largest technology businesses meet the listing and size requirements.
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S&P 500
The S&P 500 measures the large-cap segment of the U.S. equity market. It is designed to represent a cross-section of major U.S. companies rather than a single exchange or a single industry. Financial companies are eligible, as are businesses in technology, health care, industrials, consumer sectors, energy, utilities, real estate, communications and materials.
The index page from S&P Dow Jones Indices showed 503 constituents on August 31, 2026. The number of constituents can differ from the number of index securities because one company can have more than one eligible share line. Therefore, “S&P 500” does not always mean exactly 500 securities in a snapshot.
Nasdaq-100 and S&P 500 at a glance
| Feature | Nasdaq-100 | S&P 500 |
|---|---|---|
| Primary universe | Largest companies listed on Nasdaq | Large-cap U.S. equity market |
| Financial companies | Excluded by design | Included |
| Nominal index scope | 100 non-financial companies | About 500 large-cap companies; 503 constituents were reported on August 31, 2026 |
| Weighting approach | Modified market-cap weighting | Float-adjusted market-cap weighting |
| Largest sector in the March 31, 2026 comparison | Technology, 59.8% | Technology, 39.1% |
| Consumer discretionary weight on March 31, 2026 | 21.2% | 13.8% |
| Financials weight on March 31, 2026 | 0.0% | 10.2% |
| Historical profile in the cited 2007–2026 comparison | Higher return and higher volatility | Lower return and lower volatility |
The sector percentages use ICB classifications and are dated March 31, 2026. They are not permanent allocations. Market prices, rebalancing and classification changes can all alter the weights.
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How the selection rules create different holdings
Exchange listing versus market representation
The Nasdaq-100 starts with a listing requirement: eligible companies must trade on Nasdaq. It then removes financial companies and selects the largest qualifying businesses. The S&P 500 instead seeks large-cap U.S. market representation, so exchange listing is not the defining concept in the same way.
This distinction means two companies with similar size can be treated differently. A large financial company can qualify for the S&P 500 but cannot enter the Nasdaq-100 under its non-financial rule. Conversely, a large non-financial Nasdaq-listed company can be central to the Nasdaq-100 even if its industry weight is much smaller in the broad market.
Why “100 versus 500” is not a complete breadth comparison
The headline counts describe the indexes’ rules, not the exact economic exposure of every investment product that tracks them. The Nasdaq-100 has fewer constituents and excludes an entire sector, so each holding and each included industry can have a larger influence. The S&P 500 has a wider sector roster and more constituents, but it still uses capitalization weighting; its biggest companies can therefore dominate results.
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Constituent count also does not tell you how many independent risk drivers you own. Several companies may be exposed to the same technology spending cycle, advertising market, cloud-computing demand or interest-rate regime. A larger list of securities can still contain substantial common exposure.
How the weighting methods differ
Nasdaq-100: modified market-cap weighting
The Nasdaq-100 is market-cap oriented, but it is not a simple ranking in which every company’s weight is allowed to rise without adjustment. Its modified market-cap method applies index rules intended to manage the influence of the largest constituents while retaining a strong connection to company size. The precise rules are methodology-dependent, and the version effective May 1, 2026 should be used for current analysis.
S&P 500: float-adjusted market-cap weighting
The S&P 500 weights companies according to market value adjusted for the shares available to public investors. Shares held by insiders, governments or other strategic owners are treated differently from freely tradable shares. A company with a larger public float and higher market value generally receives a larger index weight.
Both approaches can produce concentration in the largest companies. The difference is that Nasdaq’s method is modified, while the S&P 500’s stated approach is float-adjusted market capitalization. You should not assume that either index gives every constituent an equal vote.
Sector exposure: the biggest practical difference
Nasdaq Global Indexes reported the following ICB sector weights on March 31, 2026:
| Sector | Nasdaq-100 | S&P 500 | What the gap can mean |
|---|---|---|---|
| Technology | 59.8% | 39.1% | Nasdaq-100 returns are more sensitive to technology valuations, earnings and capital-spending cycles. |
| Consumer discretionary | 21.2% | 13.8% | Nasdaq-100 has more exposure to economically sensitive consumer businesses and growth-oriented companies. |
| Financials | 0.0% | 10.2% | The S&P 500 includes banks, insurers and other financial companies; the Nasdaq-100 excludes them. |
The figures do not prove that technology will outperform or underperform. They show how a sector shock can affect each index differently. A sharp change in software spending, semiconductor demand, digital advertising or long-term interest rates may matter more to the Nasdaq-100 because technology occupies a larger share. A banking crisis or insurance-cycle change may matter more to the S&P 500 because it owns financial companies.
Sector labels also depend on the classification system and date. The table uses ICB classifications from the March 31, 2026 comparison, so it should not be combined casually with a later snapshot using another classification basis.
Concentration and mega-cap influence
What is documented for the S&P 500
S&P Dow Jones Indices reported that, on August 31, 2026, the S&P 500’s largest constituent represented 8.1% of the index and its ten largest constituents together represented 37.8%. Those figures show that broad sector coverage does not eliminate concentration. A small group of very large companies can materially affect the index’s daily and long-term performance.
Why a direct Nasdaq-100 concentration comparison needs matching dates
The available Nasdaq-100 and S&P 500 sector comparison is dated March 31, 2026, while the S&P 500 concentration figures above are dated August 31, 2026. Because prices and weights change, those dates are not interchangeable. A fair top-holdings comparison would use the same date, the same definition of constituent, and the same treatment of multiple share classes.
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Historical returns and volatility
Nasdaq Global Indexes compared total returns from December 31, 2007, through March 31, 2026. The figures below are provider-published historical results for that specific window:
| Measure | Nasdaq-100 | S&P 500 |
|---|---|---|
| Cumulative total return | 1,258% | 531% |
| Annualized return | 15.4% | 10.6% |
| Annualized volatility | 22.9% | 20.0% |
| Average volatility difference over the period | Nasdaq-100 volatility averaged 2.9 percentage points higher | |
| Correlation of daily returns | 93% | |
These numbers answer what happened during the selected period, not what must happen next. The higher Nasdaq-100 return was accompanied by higher volatility. A higher annualized return does not remove the possibility of severe interim losses, and a lower-volatility index can still decline substantially during a broad equity sell-off.
The 93% daily-return correlation shows that the indexes usually moved in the same direction during that period. Correlation is not identity: two assets can move together most days while producing different results because their sector weights, largest holdings and rebound speeds differ.
A separate trailing-period statistic
Nasdaq reported 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. That series uses a different date and methodology from the December 31, 2007–March 31, 2026 comparison. It should be read as a separate historical snapshot, not spliced into the table above.
Is the Nasdaq-100 riskier than the S&P 500?
On the cited historical evidence, it was more volatile. Annualized volatility was 22.9% for the Nasdaq-100 versus 20.0% for the S&P 500 over December 31, 2007, through March 31, 2026. The most plausible structural reasons are its larger technology and consumer-discretionary weights, exclusion of financials, smaller constituent count and stronger influence from large growth companies.
“Riskier” still depends on the risk being measured:
- Price volatility: The Nasdaq-100 had the higher annualized volatility in the cited comparison.
- Sector concentration: Its 59.8% technology weight makes the portfolio more dependent on one broad industry than the S&P 500’s 39.1% weight.
- Interest-rate sensitivity: Growth-oriented companies can be valued more aggressively when future earnings are discounted at low rates and pressured when rates rise, although the effect varies by company.
- Financial-sector exposure: The Nasdaq-100 has none under its stated rule, while financials made up 10.2% of the S&P 500 in the March 31, 2026 snapshot. This changes which economic shocks each index feels most directly.
- Concentration risk: Both are capitalization-weighted families of large companies, so losses in their biggest constituents can pull down the whole index.
These are structural risk channels, not guarantees. The S&P 500 can be more volatile during a particular event, and the Nasdaq-100 can outperform during a particular period. The historical comparison supports a description of past behavior, not a prediction or a suitability determination.
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Are the indexes diversified from each other?
They are different, but they are not opposites. Both hold many of the largest publicly traded companies, so an investor who already owns one may have significant exposure to the other’s biggest names. Adding both can broaden sector coverage somewhat, especially by adding financials through the S&P 500, but it can also leave the portfolio heavily exposed to the same mega-cap growth companies.
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The amount of overlap changes as companies enter or leave an index and as weights move. A specific overlap percentage is meaningful only when it is calculated from matched holdings on the same date. Without that matched snapshot, treat “owning both” as partial diversification rather than a guarantee of independent performance.
Which index fits a particular portfolio role?
When the S&P 500 may be the broader core exposure
An investor seeking a single large-cap U.S. benchmark with representation across major sectors may prefer the S&P 500’s construction. Its inclusion of financials and wider sector coverage can reduce dependence on technology relative to the Nasdaq-100, although its largest companies still have substantial influence.
When the Nasdaq-100 may be the more targeted exposure
An investor who deliberately wants greater exposure to large Nasdaq-listed non-financial companies, especially technology and consumer-discretionary businesses, may use the Nasdaq-100 as a targeted allocation. The trade-off is a narrower opportunity set and greater sensitivity to the industries and valuation regimes that dominate those holdings.
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Holding both can combine a broad large-cap benchmark with a deliberate tilt toward Nasdaq-listed growth-heavy companies. The decision should be based on the resulting portfolio weights, not on the assumption that two index names automatically provide two unrelated investments. Check the largest holdings, sector percentages and the amount of financial exposure after combining them.
How to compare an index-tracking investment before buying
The index itself is a calculation, not a brokerage account. Funds and other products that seek to track an index can differ in fees, trading costs, tax treatment, replication method, distributions and tracking error. Those product details are separate from the index methodology.
- Identify the exact benchmark. Confirm that the product tracks the Nasdaq-100 rather than the Nasdaq Composite or another Nasdaq sector index, or that it tracks the S&P 500 rather than a similarly named large-cap index.
- Read the current methodology date. For the Nasdaq-100, account for the rules effective May 1, 2026. For the S&P 500, confirm the provider’s current eligibility and float-adjustment rules.
- Inspect sector weights. Look beyond the fund name. Technology, consumer discretionary and financial exposure will determine how the portfolio behaves in different market environments.
- Check concentration. Review the largest holding and top-ten weight using a snapshot date. Do not compare a March figure with an August figure as if they were simultaneous.
- Separate index performance from product performance. A fund can trail its index because of expenses, trading friction, withholding taxes or cash management, even when it tracks correctly.
- Match the exposure to your existing holdings. If you already own broad U.S. equity funds, adding either index may increase exposure to the same mega-cap companies rather than add a wholly new source of return.
Common mistakes to avoid
- Confusing Nasdaq-100 with Nasdaq Composite: The Nasdaq-100 is specifically the 100 largest eligible non-financial Nasdaq-listed companies; the Composite is a different, broader Nasdaq-market measure.
- Calling Nasdaq-100 a pure technology index: Its technology weight was 59.8% in the cited March 31, 2026 snapshot, not 100%.
- Assuming the S&P 500 owns exactly 500 securities at all times: S&P Dow Jones Indices reported 503 constituents on August 31, 2026, and constituent companies can differ from security count.
- Equating lower historical volatility with low risk: The S&P 500 still has equity-market, valuation, company and concentration risks.
- Using past outperformance as a forecast: The 2007–2026 results are historical observations from a provider comparison, not a promise of future returns.
- Comparing undated holdings: Weights change. Always attach the measurement date and classification basis to a concentration or sector claim.
Bottom line: different exposures, substantial overlap
The Nasdaq-100 is the narrower, more technology-heavy and non-financial index. The S&P 500 is the broader large-cap U.S. benchmark, with financials and more sectors but meaningful mega-cap concentration of its own. In the official comparison covering December 31, 2007, to March 31, 2026, the Nasdaq-100 delivered higher annualized and cumulative returns, alongside higher annualized volatility. That record explains why investors may view it as a higher-growth, higher-concentration allocation; it does not establish which index will perform better next or which one is appropriate for every portfolio.
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