The judges’ cognitive flaws are not the only cause of errors in predictive judgments. Objective ignorance often plays a larger role. Some facts are actually unknowable—how many grandchildren a baby born yesterday will have seventy years from now, or the number of a winning lottery ticket in a drawing to be held next year. Others are perhaps knowable but are not known to the judge. People’s exaggerated confidence in their predictive judgment underestimates their objective ignorance as well as their biases.
