"About $25 trillion in value has been erased from stocks worldwide in the past year. The MSCI World Index of 23 developed countries lost 28 percent through Oct. 3, the worst annual performance on record dating back to 1970. Investors in the U.S. face their first annual loss in six years after the S&P 500 dropped 30 percent from its October 2007 record.

The S&P 500 is still valued at 19.5 times profit from the past four quarters, according to data compiled by Bloomberg."