Please forward this error screen to sharedip-4325515496. 47 0 0 0 13 6. Messengers from brokerage good time to invest in stock market crowd around a newspaper in New York City on October 24, 1929.

At this time 85 years ago, Yale economist Irving Fisher was jubilant. At the time he said it, in early October, he had good reason to believe he was right. 3, 1929, the Dow Jones Industrial Average swelled to a record high of 381. 17, reaching the end of an eight-year growth period during which its value ballooned by a factor of six. Fisher, consistently bullish, pronounced the slide only temporary. In his defense, he was not the only optimist on Wall Street. After witnessing nearly a decade of growth, most economists, investors, and captains of industry believed that the market’s natural direction was up.

The beginning of the crash struck them not as a sign of financial doom, but as an opportunity for bargains. Many of those optimists, including Fisher, went broke by mid-November, when the Dow had lost nearly half its pre-crash value. He went on to develop a new theory about what had triggered the crash: overly liberal credit policies that encouraged Americans to take on too much debt, as he himself had done in order to invest more heavily in stocks. By then, however, no one was listening. Read Niall Ferguson’s comparison between 1929 and 2008 here in TIME’s archives: The End of Prosperity? TIME may receive compensation for some links to products and services on this website.