“In assessing the profit of a given company, for example, people tend to assume normal operating conditions and make their estimates contingent upon that assumption,” they wrote in their notes. “They do not incorporate into their estimates the possibility that these conditions may be drastically changed because of a war, sabotage, depressions, or a major competitor being forced out of business.” Here, clearly, was another source of error: not just that people don’t know what they don’t know, but that they don’t bother to factor their ignorance into their judgments.
