Dow Divisor

What Is the Dow Divisor?

The Dow divisor is a numerical value used to calculate the level of the Dow Jones Industrial Average (DJIA). The DJIA is calculated by adding up all the stock prices of its 30 components and dividing the sum by the divisor. However, the divisor is continuously adjusted for corporate actions, such as dividend payments and stock splits.

Index divisors are commonly used in the case of a price-weighted stock market index, such as the DJIA, to generate a more manageable index value.

How the Dow Divisor Works

The Dow divisor is used to maintain the historical continuity of the DJIA index since there have been numerous stock splits, spinoffs, and changes among the Dow constituents since the index was first introduced in 1896. The Dow divisor maintains continuity by factoring in the many changes that take place within the market, such as stock splits and changes to—or payments of—dividends.

The Dow divisor is adjusted to ensure that such events do not, in and of themselves, alter the true numerical value of the DJIA. Because of major changes that have taken place within the market, the value of the Dow divisor has changed significantly over the years. For example, it was at 16.67 back in 1928 and as low as 0.147 as of Sept. 2019. 

As of December 2021, the divisor for DJIA is 0.15172752595384, but each Dow Jones index has its own divisor, such as the Dow Jones 20 Transport and Dow Jones 15 Utilities.

The Dow is named after Charles Dow, a founding editor of The Wall Street Journal, who, in 1896, partnered with statistician Edward Jones to form the first version of the DJIA. Since this time, The Wall Street Journal has been tasked with ensuring that the Dow divisor is adjusted properly to maintain the DJIA’s historical accuracy. 

Special Considerations 

Events such as stock splits or changes in the list of the companies composing the index can often alter the sum of the component prices. In these cases, and in order to avoid discontinuity in the index, the Dow divisor is updated so that the quotations right before and after the event coincide. 

Most corporate actions, such as stock splits and spinoffs, have served to push the value of the Dow divisor lower. At first, the Dow divisor was composed of the original number of DJIA companies, which made the DJIA a simple arithmetic average. However, as certain events have taken place to alter the overall value of the market, the Dow divisor has been manually altered in order to ensure that the DJIA is accurately valued. 

The divisor fell below 1.0 in 1986 for the first time. The present divisor, after many adjustments, is less than one, which means the index is larger than the sum of the prices of the components. The fact that the divisor is now well below one means that the divisor now functions as a multiplier, rather than a divisor.

Example of the Dow Divisor

Let's say you sum up the prices of the 30 constituents of the DJIA and arrive at 5,498.07. Assume that the Dow divisor is set at 0.15172752595384: using this divisor, every $1 change in price in a particular stock within the average equates to a 6.59 (or 1 ÷ 0.15172752595384) point movement.

Dividing the price total of 5,498.07 by the Dow divisor of 0.15172752595384 would provide a level of 36,236.47 for the index. Note to divide the price total by the divisor and not the number 30, which is the number of names in the index.