The Dow Jones Industrial Average is the index most people have heard of, quoted on news bulletins for more than a century. Yet many traders regard it as the least representative of the big American benchmarks. Understanding why tells you a lot about how stock indices are built and why they can tell different stories on the same day.
What the Dow is
The Dow, as it is usually called, tracks 30 large US companies chosen by a committee at S&P Dow Jones Indices. It was created in 1896 by Charles Dow, co-founder of the Wall Street Journal, and originally contained 12 mostly industrial firms. Today its members span technology, banking, healthcare, retail and consumer goods, and the word industrial is a historical leftover.
Why it is price-weighted
The Dow’s most important quirk is that it is price-weighted. A company’s influence depends on its share price, not on its size. A stock trading at $500 a share moves the index far more than one trading at $50, even if the cheaper share belongs to a much bigger company.
Most modern indices, including the S&P 500 and the FTSE 100, are weighted by market capitalisation, so the largest companies have the biggest say. That is generally considered a better reflection of where investors’ money actually sits.
The Dow is calculated by adding up the prices of its 30 shares and dividing by a figure called the Dow divisor, which is adjusted over time for stock splits and changes in membership so the index does not jump for reasons unrelated to the market.
How it differs from the S&P 500 and Nasdaq
Because it holds only 30 names and weights them by price, the Dow can diverge sharply from broader indices. It tends to be heavier in established, dividend-paying businesses and lighter in the high-growth technology names that dominate the Nasdaq.
That difference showed up clearly on 22 October 2026. The Nasdaq Composite fell 2.6 per cent and the S&P 500 1.2 per cent as investors sold big technology stocks, but the Dow finished almost exactly flat. For anyone reading the headlines, the message was that the selling was concentrated in tech rather than spread across corporate America. Our Morning Market Brief unpacked what that meant for the next session.
Why traders still watch it
Despite its flaws, the Dow matters. It is followed by millions of people, it has deep and liquid futures markets, and its long history makes it useful for comparing market behaviour across decades. Many UK traders trade the Dow through futures or contracts for difference, often called the Wall Street 30 or US30 on trading platforms.
Things to keep in mind
Big point moves in the Dow sound dramatic because the index is at a high level. A 500-point fall may be less than 1 per cent. Always think in percentages rather than points. And remember that a single high-priced member can move the index on company-specific news that says little about the wider market.
The bottom line
The Dow is Wall Street’s oldest gauge and still one of its most quoted. It is best used alongside the S&P 500 and Nasdaq rather than on its own, because the gaps between them often reveal where money is really moving. If you want to understand your own strengths and gaps as a trader, take the free Samuel & Co Trading Trader Assessment.
