“[M]y own common sense taught me that the human being is yet to be born who can make a rigid plan covering twelve months in the future without running into the danger of suddenly operating a plan instead of a business. If it were possible to plan for a year ahead, then there would be no need for judgment or management—any question that came up could be settled by referring to the plan. That is the trouble with a plan, especially a carefully considered plan. We are so likely by tacking the name ‘‘plan’’ on what is only a guess to give more dignity and weight to the plan than it deserves.
[At Firestone] we do the best we can to forecast, but we never fool ourselves into holding this forecast to be anything more than a guess … There is nothing wrong about guessing in business, unless you call it “estimating” and attach an undue importance to it. I want to know when I am guessing and when I am dealing with facts.”
— Harvey Firestone in Men and Rubber: The Story of Business
Lightly edited for clarity.