> are supposed to be under control now Why would you think that? Massive swing effects are often caused or exacerbated by algorithms trading on momentum. They

> are supposed to be under control now Why would you think that? Massive swing effects are often caused or exacerbated by algorithms trading on momentum. They do that because trading on momentum usually pays, and doing the hard work of fundamental value investing is difficult and also hard to scale. Momentum trading is fine if only a few people are doing it, but if enough of the market transitions to having 'no opinion except following the crowd', then you get instability just like this. And many factors since 2010 have made flash crash-like events easier to cause, not harder.