Nasdaq vs. S&P 500 vs. Dow: How the Major U.S. Stock Indexes Differ

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The Dow Jones Industrial Average, the S&P 500 and the Nasdaq Composite are the three most widely quoted U.S. stock market indexes. They differ in three ways that matter. They hold different numbers of stocks (30, about 500 and more than 3,000). They choose those stocks by different rules (a committee’s judgment, a committee working from published financial criteria, and a simple exchange-listing requirement). And they weight their members differently: the Dow by share price, the other two by market value.

Nasdaq vs. S&P 500 vs. Dow: Key Differences

How Each Index Works

The Dow Jones Industrial Average

Charles Dow, co-founder of Dow Jones & Company and The Wall Street Journal, first published the average on May 26, 1896. It began as a plain average of 12 industrial stock prices: add the prices, divide by 12. The index expanded to 30 stocks in 1928 and has stayed at that size.

The “Industrial” in the name is now historical. Today’s Dow includes technology, financial, healthcare, retail and consumer companies. Transportation and utility stocks sit in the separate Dow Jones Transportation Average and Dow Jones Utility Average. Membership is decided by the Averages Committee at S&P Dow Jones Indices. There are no fixed numerical cutoffs and no set review schedule. The committee looks for large U.S. companies with strong reputations, sustained growth and interest to a broad group of investors. It also tries to keep a reasonable sector balance.

The index is calculated as:

Dow = sum of the 30 share prices ÷ Dow divisor

The divisor started as the number of stocks. Over time it has been adjusted every time a member splits its stock, pays a special dividend or is replaced, so that those events do not cause an artificial jump in the index. After more than a century of adjustments, the divisor sits well below 1. As a result, a $1 change in any one member’s share price moves the Dow by several points, and that $1 counts the same no matter which company it belongs to.

The S&P 500

Standard & Poor’s expanded its stock index to 500 companies in March 1957; S&P Dow Jones Indices now maintains it. Its members represent about 80% of the total market value of U.S. listed stocks. Because a few companies issue more than one share class (Alphabet’s GOOGL and GOOG, for example), the index usually holds slightly more than 500 securities.

The S&P 500 uses float-adjusted market-cap weighting:

Company weight = (share price × shares available to public investors) ÷ total float-adjusted value of all members

“Float-adjusted” means that shares held by insiders, governments or other strategic holders, which rarely trade, are left out of the count. The index level itself is the total float-adjusted market value of all members divided by a separate divisor. That divisor is adjusted for share issuance, buybacks and membership changes so the index moves only with prices.

The Nasdaq Composite

Nasdaq opened in 1971 as the world’s first electronic stock market, and the Composite launched with it on February 5, 1971, at a base value of 100. Unlike the other two indexes, the Composite has no selection committee. With narrow exceptions, any eligible security listed on the Nasdaq Stock Market is included. That covers common stocks, American Depositary Receipts (ADRs), real estate investment trusts (REITs), tracking stocks and limited partnership interests. Funds such as ETFs are excluded. Foreign companies listed on Nasdaq count, so the Composite is not a purely U.S. index.

Like the S&P 500, the Composite is market-cap weighted. Because Nasdaq became the listing venue for many of the largest technology companies, those companies make up a large share of the index’s value. That share is what gives the Composite its technology tilt. It also holds thousands of small companies, many of them biotech and other early-stage firms, but their combined weight is small next to the largest members.

Worked Example: How Weighting Changes the Result

The same price moves can produce different index results depending on the weighting method. Imagine a three-stock market (the figures are hypothetical and show only the mechanics):

Price-weighted (Dow-style). Sum of prices = $475. With a divisor of 3, the index reads 158.33. Stock A makes up 400 ÷ 475, or about 84% of the index, even though it is a mid-sized company here.

Market-cap weighted (S&P 500 and Nasdaq style). Total value = $150 billion. Stock B carries 100 ÷ 150, or about 67%. Stock A carries about 27%. Stock C carries about 7%.

Now suppose Stock A rises 10% to $440 and Stock B falls 10% to $45. Stock C is unchanged.

• Price-weighted: new sum = $440 + $45 + $25 = $510. The index rises to 170.00, a gain of about 7.4%.
• Market-cap weighted: new total = $44 billion + $90 billion + $10 billion = $144 billion. The index falls about 4.0%.

The same day produces opposite headlines: the price-weighted index follows the highest-priced stock, the cap-weighted index the most valuable company. Real indexes rarely diverge this much because their members overlap. When a few heavily weighted stocks move sharply, though, this gap is why the Dow and the S&P 500 can close in different directions.

What a Stock Split Does

A split shows the price-weighting quirk clearly. When a Dow member splits 4-for-1, its share price drops to a quarter of its prior level. The divisor is adjusted so the index level does not change at the moment of the split. From then on, though, the company’s influence on the Dow is roughly a quarter of what it was. Nothing about the business has changed.

Apple’s 4-for-1 split in August 2020 cut its Dow weight in exactly this way. In a cap-weighted index, a split changes nothing: price falls, share count rises, and market value is the same. This is also why the Dow committee considers share price when adding a company. A stock with a very high price would dominate the average, and one with a very low price would barely register.

How Companies Get Into Each Index

Dow Jones Industrial Average

The Averages Committee chooses members at its discretion, with no fixed thresholds for market cap, revenue or earnings and no regular calendar. Changes often accompany an acquisition, a spin-off or a shift in a company’s relevance. The committee weighs share price and how well the 30 members together reflect the U.S. economy.

S&P 500

The U.S. Index Committee also has discretion, but it works from published eligibility rules:

• Market capitalization: a company must meet a minimum market cap. The threshold is raised over time as markets grow and was set at $22.7 billion in a recent methodology update.
• Liquidity: the stock must trade actively relative to its float, so the index can be replicated without large price impact.
• Profitability: the sum of the most recent four quarters of GAAP earnings must be positive, and so must the most recent quarter.
• Public float: enough shares must be available to public investors.
• Domicile and listing: the company must be U.S.-domiciled and listed on an eligible U.S. exchange (NYSE, Nasdaq or Cboe).
• Sector balance: the committee considers how an addition affects sector representation.

Meeting these rules makes a company eligible. It does not guarantee a spot, since the committee chooses among eligible candidates when an opening appears. The index is rebalanced quarterly, and members can be replaced at any time.

Nasdaq Composite

Membership is automatic for eligible security types listed exclusively on the Nasdaq Stock Market, with limited exceptions. Market cap and profitability requirements do not apply, so a newly listed, unprofitable company can enter the Composite. The same company might wait years to qualify for the S&P 500, or never qualify.

Historical Performance Patterns

Over long periods all three indexes have risen. Each has also suffered severe drawdowns, and the worst episodes show how their construction shaped the damage. The headline index levels are price indexes: they leave out dividends. Total return versions, which assume dividends are reinvested, show higher long-run results. The gap matters most for the S&P 500 and the Dow, whose members tend to pay larger dividends than the average Nasdaq-listed company.

The Dow: Depression-Era Collapse and Postwar Climb

The Dow fell about 89% from its September 1929 peak to its July 1932 low. On October 28, 1929, it lost nearly 13% in one session. The index did not regain its 1929 high until 1954, a quarter century later. On October 19, 1987, it fell about 22.6% in a single day, still its largest one-day percentage decline. Between those crashes came long advances, including a steady rise through the 1950s and early 1960s as postwar consumer spending and industrial output grew.

The S&P 500: The 1980s-1990s Boom and the 2008 Crisis

The S&P 500 gained strongly through the 1980s and 1990s. Price gains averaged around 14% a year across those two decades, helped by falling interest rates, lower inflation, deregulation and technology-driven productivity growth. In the 2007 to 2009 financial crisis, the index dropped about 57% from its October 2007 peak to its March 2009 low as the subprime mortgage collapse hit banks and the wider economy. A long bull market followed, supported by monetary stimulus and recovering corporate earnings.

The Nasdaq Composite: The Dot-Com Bubble and the Pandemic Rally

The Composite rose more than 400% from 1995 to its March 2000 peak as investors poured money into internet and technology companies. It then fell roughly 78% through late 2002. It did not close above its 2000 high again until 2015, about 15 years later.

The index had a similar but milder run in the pandemic era. It climbed about 125% from its March 2020 low to its November 2021 peak as demand for e-commerce, cloud computing and remote-work services lifted its largest members.

These episodes share a pattern. When growth and technology stocks lead, the Nasdaq Composite tends to rise fastest, and when they fall, it tends to fall hardest. The S&P 500’s broader mix of financial, industrial, energy, healthcare and consumer staples companies has usually softened its swings. The Dow’s 30 members, picked partly for stability, give it a different profile, though one high-priced member can still drive the index.

How Investors and Traders Use Each Index

As a market gauge. News coverage reports all three, but they answer different questions. The S&P 500 is the closest single measure of how large U.S. companies as a group are doing. The Nasdaq Composite shows how Nasdaq-listed, largely growth-oriented stocks are faring. The Dow shows how a hand-picked group of blue-chip companies performed, filtered through price weighting.

As a benchmark. Most U.S. large-cap mutual funds and many investors’ portfolios are compared with the S&P 500, usually over a set window such as year-over-year or five-year returns. Comparing a diversified portfolio with the Dow or the Nasdaq Composite can mislead, because neither represents the broad market’s sector mix. For the total U.S. market, including small caps, investors use broader total-market indexes.

As an investment. You cannot buy an index directly, only products that track it. S&P 500 index funds and ETFs (SPY is the best-known ETF ticker) are among the most widely held investment products. Dow-tracking funds exist, and they hold the 30 stocks in proportion to their price weights. Funds tracking the full Nasdaq Composite exist but are far less common. The well-known “Nasdaq” ETF, QQQ, tracks the Nasdaq-100 instead.

As a trading instrument. Futures, options and CFDs are written on these benchmarks. On many CFD and prop-trading platforms, US30 refers to the Dow, US500 to the S&P 500 and US100 (or NAS100) to the Nasdaq-100, not the Composite. US100 and US500 charts often look similar because they share heavyweight stocks, but US100 moves tend to be larger in percentage terms, reflecting its narrower, tech-concentrated membership.

As a style signal. Investors who want growth and technology exposure and can accept larger drawdowns often look to Nasdaq-based products. Those wanting a core holding that tracks the broad large-cap market typically use the S&P 500. Investors focused on established, often dividend-paying companies sometimes favor Dow-based products, though the S&P 500 holds those same companies and many more.

Distinctions Readers Often Confuse

Nasdaq the Exchange, the Composite and the Nasdaq-100

“Nasdaq” can mean three things. Nasdaq is a stock exchange operator. The Nasdaq Composite is its broad index of more than 3,000 Nasdaq-listed securities. The Nasdaq-100 (ticker NDX), launched in 1985, holds roughly the 100 largest non-financial companies listed on Nasdaq and uses a modified market-cap weighting that caps the biggest weights. When a headline says “the Nasdaq rose 1%,” it usually means the Composite. When a trader says “NAS100” or “the Nasdaq,” they often mean the Nasdaq-100.

There Is No “Nasdaq 500”

No major index is called the Nasdaq 500. The confusion usually comes from blending “Nasdaq” and “S&P 500.” The S&P 500 is not a Nasdaq index. It includes companies listed on both the NYSE and Nasdaq.

How Much the Indexes Overlap

The overlap is large at the top. Many of the most valuable U.S. companies are listed on Nasdaq and belong to the S&P 500, so they rank among the heaviest weights in both. Dow members, as large U.S. companies, are typically S&P 500 members too, though no rule requires it. The Composite is not a subset of the S&P 500: most of its members are far too small or are foreign companies. The S&P 500, in turn, holds hundreds of NYSE-listed companies the Composite never includes.

This shared top tier is why the three usually move in the same direction. How closely they track each other still depends on which sectors lead, and it varies with market conditions.

Points vs. Percentages

The Dow’s index level is many times the S&P 500’s, so the same percentage move produces far more Dow points. A 1% move in a hypothetical Dow at 40,000 is 400 points. A 1% move in a hypothetical S&P 500 at 5,000 is 50 points. A “400-point drop” and a “50-point drop” can describe the same percentage decline. Compare indexes only in percentage terms.

Ticker Symbols

SPX and INX are the S&P 500 index; SPY is an ETF that tracks it. NDX is the Nasdaq-100. Mixing up an index with a fund that tracks it is common, but the fund’s price, fees and dividends differ from the index’s level.

Limitations of Each Index

The Dow. Price weighting has no economic basis. Influence depends on share price, not size, so a split or a high share price can shift the index’s makeup with no change in the business. Thirty stocks cannot capture the breadth of the U.S. market, whole sectors carry little or no weight, and committee discretion makes changes harder to predict than rule-based additions.

The S&P 500. Market-cap weighting means the index becomes more concentrated as its largest companies grow. A few very large members can account for a large share of its total value, so it is less diversified than “500 companies” suggests. It also covers only large-cap stocks, leaving out the small- and mid-cap segment, and the committee keeps some discretion over who joins.

The Nasdaq Composite. Its makeup reflects where companies chose to list rather than any judgment about what represents the economy. Technology dominates, while sectors such as energy and utilities are underrepresented because fewer of those companies list on Nasdaq. With no profitability or size screen, it includes many speculative companies, and cap weighting concentrates it in its largest members, which have historically made it the most volatile of the three.

All three. The headline levels exclude dividends, they measure only stocks (not bonds or other assets), and none of them is a direct reading of the U.S. economy. Stock prices reflect expectations about corporate profits, which can diverge from current economic data for long stretches.

FAQs

The Bottom Line

Investors choosing a benchmark or an index fund need to know what each index measures. The S&P 500 is the closest single gauge of large U.S. companies and the usual yardstick for diversified portfolios. The Nasdaq Composite tilts toward technology and has historically swung further, while the price-weighted Dow reflects 30 hand-picked blue chips. Compare any of them by percentage change, never by points.