Black Tuesday "Stock Market Crash"
A stock market crash is a sudden dramatic decline of stock prices across a significant cross-section of a stock market, resulting in a significant loss of paper wealth. Crashes are driven by panic as much as by underlying economic factors. They often follow speculative stock market bubbles
Stock market crashes are social phenomena where external economic events combine with crowd behavior and psychology in apositive feedback loop where selling by some market participants drives more market participants to sell. Generally speaking, crashes usually occur under the following conditions. a prolonged period of rising stock prices and excessive economic optimism, a market where P/E ratios exceed long-term averages, and extensive use of margin debt and leverage by market participants.