1) Margin debt – the amount of money that investors have borrowed in order to buy stocks – is now at the highest level in history, not only in absolute terms, but also relative to U.S. GDP.
2) The present ratio of total U.S. equity market capitalization to GDP is 2.63. (as in: 263%!)
The historical norm (not the low!) is 0.78. (Which is about 70% below the current level.)
that should end up being a little difference without much distinction.
However, where the difference between equity indexes is likely to be (remain) substantial, as well as what is to continue to be the best equities-based trade out there, is this one;
SHORT the DJIA/Nikkei225 spread.