The dangers of wishful thinking...
While the crash only took place 6 months ago, I am convinced we have now passed through the worst--and with continued unity of effort we shall rapidly recover. There has been no significant bank or industrial failure. That danger, too, is safely behind us.
Herbert Hoover, May 1, 1930.
The Great Depression is generally recognized to have lasted another 10 years, with US GNP not reaching 1929 levels again until 1940. The Dow Jones Industrial Average also proceeded to drop roughly 85% in the 24 months immediately following this comment.