Bulkowski’s Factors Influencing Stocks

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Written by and copyright © 2005-2008 by Thomas N. Bulkowski. All rights reserved.

How important are market and industry trends in influencing the behavior of your stock? Many people have asked that question, and this page provides at least part of the answer.

This is from the book, Investment Analysis and Management, by Stanley Huang, published in 1981 by Winthrop Publishers, Inc.

Here are the results from research on the influence of several factors on stock price changes.

Influencing Factor Percentage
Economy-wide 30% to 35%
Company 30% to 35%
Industry 15% to 20%
Other 15% to 20%

Huang cites a study done by Richard A. Brealey in An Introduction to Risk & Return from Common Stocks, published by M.I.T. Press in 1969. I averaged the results of the 63 stocks in 6 industries that he shows, covering the period from 1952 to 1960. Here’s what I found.

Influencing Factor Percentage Min/Max
General market 31% 1%/66%
Company (stock) 20% 6%/42%
Industry 12% 0%/24%
Other 37% 13%/72%

Although the results are decades old, they do provide some idea of how important it is to consider the market and industry trends when trading stocks. The first category, general market, is an influence that affects all stocks. The company (stock) influences are factors that pertain to one stock. An industry influence is one that affects all stocks in the same industry. The ‘other’ category includes a variety of influences that are not industry specific.

Notice how important the general market is to the price fluctuation of common stocks – 31%. Think of this as the importance of general economic conditions to stock behavior. What surprises me are the low 12% attributed to industry specific influences and 20% for stock (company specific) influences.

Copyright © 2005-2008 by Thomas N. Bulkowski. All rights reserved. Cannibal: A guy who goes into a restaurant and orders the waiter.