Getting to the Point of a Point

Written by Dimensional Fund Advisors.

March 2019

A quick online search for “Dow rallies 500 points” yields a cascade of news stories with similar titles, as does a similar search for “Dow drops 500 points.”

These types of headlines may make little sense to some investors, given that a “point” for the Dow and what it means to an individual’s portfolio may be unclear. The potential for misunderstanding also exists among even experienced market participants, given that index levels have risen over time and potential emotional anchors, such as a 500-point move, do not have the same impact on performance as they used to. With this in mind, we examine what a point move in the Dow means and the impact it may have on an investment portfolio.

IMPACT OF INDEX CONSTRUCTION

The Dow Jones Industrial Average was first calculated in 1896 and currently consists of 30 large cap US stocks. The Dow is a price-weighted index, which is different than more common market capitalization-weighted indices.
An example may help put this difference in weighting methodology in perspective. Consider two companies that have a total market capitalization of $1,000. Company A has 1,000 shares outstanding that trade at $1 each, and Company B has 100 shares outstanding that trade at $10 each. In a market capitalization-weighted index, both companies would have the same weight since their total market caps are the same. However, in a price-weighted index, Company B would have a larger weight due to its higher stock price. This means that changes in Company B’s stock would be more impactful to a price-weighted index than they would be to a market cap-weighted index.

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