40% Market, 30% Sector, 30% Stock

Steven A. Cohen (about 1956 - ), a legendary stock trader, was interviewed in Jack Schwager's Stock Market Wizards.

Jack: Did your economics education at Wharton help at all in your career as a stock trader?
Cohen: Not much. A few things they taught you were helpful.

Jack: Like what?
Cohen: They taught you that 40 percent of a stock's price movement was due to the market, 30 percent to the sector, and only 30 percent to the stock itself, which is something that I belive is true. I don't know if the percentages are exactly correct, but conceptually the idea makes sense.

From: Jack D. Schwager, Stock Market Wizards, Harper Business, 2003, p.269.