Why Is the Dow Price-Weighted?

The formula

In simplified form, the Dow level equals the sum of the component share prices divided by the Dow divisor. The divisor is maintained by S&P Dow Jones Indices and adjusted for specified events so corporate actions and component changes do not create an artificial jump in the index.

This is why a $1 move in any one component changes the price-sum numerator by the same $1, before division by the current divisor. The company's market capitalization does not set its Dow weight.

A two-stock illustration

Imagine two hypothetical Dow constituents priced at $400 and $40. If each rises by $2, each adds the same $2 to the sum of component prices. The $2 change therefore has the same index-point effect for both under the same divisor, even though the lower-priced stock's percentage return is much larger.

This illustration uses no actual Dow divisor and is not a historical market example.

How this differs from market-cap weighting

In a float-adjusted market-cap-weighted index, influence depends on a constituent's float-adjusted market value. In a price-weighted index, influence depends on its share price relative to the other component prices. A stock split can therefore require a divisor adjustment to preserve continuity.

What the website shows

The website's illustrative Dow hero covers all 30 constituents and identifies its engine as price-weighted. DIA fund holdings can serve as a separate ETF reference, but those fund weights are not the Dow's official price-based constituent weights. The current Windows app offers an S&P 500 basket; a Dow workspace is planned.