"The Depression was an economic catastrophe unmatched before or since. It was signalled by a collapse in American asset prices. On October 29, 1929 - 'Black Tuesday' - the Dow Jones Industrial index fell by nearly 12 per cent, one of the steepest one-day declines in its history. The market had in fact begun to slide after September 3; by November 13 it had fallen by nearly 50 per cent. This signified a slump in the confidence of investors in the future profitability of US corporations, magnified by panic selling on the part of speculators who had been trading on margin (in effect, with borrowed money). The subsequent rally, which lasted until April 1930, proved illusory. From then until July 1932 the market slid inexorably downwards. At its nadir on July 8, 1932 stock prices had fallen to just 11 per cent of their 1929 maximum. With the exception of 1914, the stock market had never seen such volatility, and nothing remotely like it has happened since."