There has been so many explanations for the great depression which began in the United States and swept across other industrialised countries; but a major fall in stock price seems to be the one single explanation that has stood the test of time. In the 1920s the U.S. stock market experienced a rapid expansion, reaching its zenith in August 1929. Stock prices began to decline in September and early October, but the fall began Oct. 18. Panic set in, and on October 24, a record 12,894,650 shares were traded. Investment companies and leading bankers attempted to stabilize the market by purchasing great blocks of stock; they were trying to mitigate the steep decline. However, on Monday, the storm broke loose, and the market went into a free fall. The great depression was the longest, deepest, and most widespread depression of the 20th century.