These charts help us understand that a top is not just price, but a reversal in extremes of margin debt, valuation and sentiment.
In blow-off tops, extremes of valuation, complacency and margin debt can always shoot beyond previous extremes to new extremes. This is why guessing when the blow-off top implodes is so hazardous: extreme can always get more extreme.
Nonetheless, extremes eventually reverse, and generally in rough symmetry with their explosive rise. Exhibit 1 is margin debt: NYSE Margin Debt Hits a New Record High (Doug Short)
Note the explosive rise in margin debt in the past few months: