Yeah, until it doesn't, VXX just isn't convinced of the sell off , yet. More correctly , VIX is not convinced , and more granular still what VIX represents , the ratio of short to Med term puts and calls on the SP 500 . Once the market is convinced there is s potential for real down on SP 500 or SPY , then you will see a gradual to sudden shift to puts on SP , that will be conveyed in the price of VIX and VXX .