NDX up, SPX down
Big tech stocks helped drive the Nasdaq 100 (NDX) to more than a 1% gain on Monday, while the S&P 500 (SPX) fell more than 1%. This has never happened before. There were 6 times when NDX gained 0.75% while SPX lost at least that much. All but one of them saw stocks drop over the next 1-2 weeks, but all of them showed a gain either 2 or 3 months later, for what it's worth. The dates were 1996-12-11, 1999-01-11, 2000-01-03, 2000-04-28, 2000-06-16, and 2001-10-18.
