I like this missive from JP MORGAN’s outstanding research department.

“Meanwhile it would be easier to feel better about the SPX if its leadership wasn’t so thin – the “FANG” complex (FB/AMZN/NFLX/GOOG) continues to do a ton of heavy lifting (along w/stocks like MSFT, GE, and HD).  The SPX is up ~25 points in ’15 but AMZN and GOOG/GOOGL are contributing ~30 points to the index all by themselves (MSFT is adding 8 points, FB 6.8, GE 5.8, and HD 4.3).  Meanwhile, the violent daily market swings shouldn’t be considered a virtue and instead are a sign of the enormous influence non-fundamental factors continue to hold over trading.”