Wild: The top 5 stocks in the $NDX 100 comprise 52% of the index's combined market cap. The top 2 stocks, $NVDA & $MSFT, with $8 trillion in combined market cap, represent 27% of the index. Even wilder: Since the April lows both stocks show a 95% directional price correlation.

How unusual is this? Very. Look back a couple of years & you can see how the complete lack of variability in the correlation since April stands out. The combined market cap expansion in a virtual straight line awe inspiring. Sustainability? I'll leave that for you to debate ;-)