In 1949, the total value of listings on the New York Stock Exchange was $150 billion. In 1984, the total value of all US public equities was $2 trillion. In 2005, the total value of Big Board listings was $20 trillion, plus $3 trillion listed on NASDAQ.
Then, from Oct 2007 – Oct 2008, US stock market capitalization lost $7 trillion.
various sources including several versions of The Intelligent Investor