An Experiment in Probabilistic Forecasting

by Thomas A. Brown

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Describes an experiment in forecasting economic, political, and military events, expressing uncertainty with explicit probabilities. The subjects were 31 UCLA summer students: 16 graduate students, 14 upper classmen, and one freshman, of both sexes, ages ranging from 18 to 41, with a wide variety of majors. The questions, asked in July 1970, called for forecasts of December 1970 quantities. Almost all the respondents were able to answer in probabilistic terms. Results were scored when the factual outcomes were known. It was found that, as in other experiments, the true answers tended to appear in the tails of the distribution. Several consensus averaging techniques were used to overcome this problem; the most effective was the probability density technique. Four subjects, out of 31, were able to outscore the consensus: two male seniors, majoring in history and economics, and two female graduate students majoring in counselor education and opera.

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