KEY POINTS
  • The size of the stock market relative to the size of the economy is at an all-time high.
  • The cyclically adjusted price-to-earnings ratio, created by Nobel Prize winner Robert Shiller, is near the highest since 2000 dot-com bubble.
  • "That the bulk of last year's returns came from higher valuations, and not growth in earnings, only compounds investors' concerns," Goldman Sachs Investment Strategy Group CIO Sharmin Mossavar-Rahmani said in the group's 2020 outlook.

The size of the stock market relative to the size of the economy is at its highest level ever, raising concerns that the market's recent all-time highs are detached from reality.

The likes of legendary investors Warren Buffett and Paul Tudor Jones have measured the stock market in this, or similar ways in the past to determine if it is overvalued or undervalued.