The cyclically adjusted price-to-earnings (CAPE) ratio is a valuation metric typically used to gauge whether entire stock market indexes are overvalued or undervalued. It was developed by Nobel-winning economist Robert Shiller during the dot-com bubble, so it is sometimes referred to as the Shiller P/E ratio.

Investing legend Warren Buffett is clearly not someone who has to rely on Social Security, given that he has billions of dollars in wealth. However, the financial giant is aware that millions of older Americans today depend on those monthly benefits to make ends meet.

Perhaps that’s one reason stocks are selling off globally this morning. While most indexes in Asia and Europe remain near their all-time highs, there is broad-based but mild selling in all of them.