Charles H. Dow says that to understand the stock market study business conditions
"We believe that the stock market as a whole should be regarded always as an effect of general conditions, and that the way to study the stock market, as a whole, is to study general business conditions (May 26, 1900)."
Who was Charles H. Dow?
“Charles Henry Dow was an American journalist who co-founded Dow Jones & Company with Edward Jones and Charles Bergstresser. Dow also founded The Wall Street Journal, which has become one of the most respected financial publications in the world. He also invented the Dow Jones Industrial Average as part of his research into market movements. He developed a series of principles for understanding and analyzing market behavior which later became known as Dow theory, the groundwork for technical analysis (source: Wikipedia.org).”