On May 6, 2010, the Dow Jones Industrial Average suffered its fastest nosedive ever. What happened? What's clear is that high-frequency trader accelerated the free fall by withdrawing from the market en masse. Four years after they caused the "Flash Crash," those speed demons still rule our financial markets.
We can just make stuff up with aplomb. One day we say the market rises as "investors cheer" good employment numbers; the very next day we attribute the decline to "structural problems" and look forward to a long decline! Were those structural problems not present yesterday when investors were cheering?