Mr. Mellon did not know. Neither did any of the other public figures who then, as since, made similar statements. These are not forecasts; it is not to be supposed that the men who make them are privileged to look further into the future than the rest. Mr. Mellon was participating in a ritual which, in our society, is thought to be of great value for influencing the course of the business cycle. By affirming solemnly that prosperity will continue, it is believed, one can help insure that prosperity will continue. Especially among businessmen the faith in the efficiency of such incantation is very great."
--John Kenneth Galbraith, The Great Crash