When the WSJ provides us with the least plausible explanation of the "Crash of 2:45 p.m.", it is only fitting that Jon Stewart provides us with the most succinct and accurate diagnosis of the crash.

Most explanations of the crash either focus on the proximate cause of the crash or blame it all on the "perfect storm". The "perfect storm" explanation absolves us from analysing the crash too closely, the implicit conclusion being that such an event doesn't occur too often and not much needs to or can be done to prevent its recurrence. There are two problems with this explanation. For one, it violates Occam's Razor - it is easy to construct an ex-post facto explanation that depends upon a confluence of events that have not occurred together before. And more crucially, perfect storms seem to occur all too often. As Jon Stewart put it: "Why is it that whenever something happens to the people that should’ve seen it coming didn’t see coming, it’s blamed on one of these rare, once in a century, perfect storms that for some reason take place every f--king two weeks. I’m beginning to think these are not perfect storms. I’m beginning to think these are regular storms and we have a sh--ty boat."

The focus on proximate causes ignores the complexity and nonlinearity of market systems. Michael Mauboussin explained it best when he remarked: "Cause and effect thinking is dangerous. Humans like to link effects with causes, and capital markets activities are no different. For example, politicians created numerous panels after the market crash in 1987 to identify its “cause.” A nonlinear approach, however, suggests that large-scale changes can come from small-scale inputs. As a result, cause-and-effect thinking can be both simplistic and counterproductive." The true underlying causes may be far removed from the effect, both in time and in space and the proximate cause may only be the “straw that broke the camel’s back”.

So what is the true underlying cause of the crash? In my opinion, the crash was the inevitable consequence of a progressive loss of system resilience. Why and how has the system become fragile? A static view of markets frequently attributes loss of resilience to the presence of positive feedback processes such as margin calls on levered bets, stop-loss orders, dynamic hedging of short-gamma positions and even just plain vanilla momentum trading strategies - Laura Kodres' paper here has an excellent discussion on "destabilizing" hedge fund strategies. However, in a dynamic conception of markets, a resilient market is characterised not by the absence of positive feedback processes but by the presence of a balanced and diverse mix of positive and negative feedback processes.

Policy measures that aim to stabilise the system by countering the impact of positive feedback processes select against and weed out negative feedback processes - Stabilisation reduces system resilience. The decision to cancel errant trades is an example of such a measure. It is critical that all market participants who implement positive feedback strategies (such as stop-loss market orders) suffer losses and those who step in to buy in times of chaos i.e. the negative-feedback providers are not denied of the profits that would accrue to them if markets recover. This is the real damage done by policy paradigms such as the "Greenspan/Bernanke Put" that implicitly protect asset markets. They leave us with a fragile market prone to collapse even with a "normal storm", unless there is further intervention as we saw from the EU/ECB. Of course, every subsequent intervention that aims to stabilise the system only further reduces its resilience.

As positive feedback processes become increasingly dominant, even normal storms that were easily absorbed earlier will cause a catastrophic transition in the system. There are many examples of the loss of system resilience being characterised by its vulnerability to a "normal" disturbance, such as in Minsky's Financial Instability Hypothesis or Buzz Holling's conception of ecological resilience, both of which I have discussed earlier.

The Role of Waddell & Reed

In the framework I have outlined above, the appropriate question to ask of the Waddell & Reed affair is whether their sell order was a "normal" storm or an "abnormal" storm? More specifically, pinning the blame on a single order requires us to prove that each time in the past an order of this size was executed, the market crashed in a similar manner. It is also probable that the sell order itself was a component of a positive feedback hedging strategy and Waddell's statement that it was selling the futures to "protect fund investors from downside risk" confirms this assessment. In this case, the Waddell sell order was an endogenous event in the framework and not an exogenous shock. Mitigating the impact of such positive feedback strategies only makes the system less resilient in the long run.

As Taleb puts it: "When a bridge collapses, you don’t look at the last truck that was on it, you look at the engineer. You’re looking for the straw that broke the camel’s back. Let’s not worry about the straw, focus on the back." Or as Jon Stewart would say, let's figure out why we have a sh--ty boat.


Sunday links: electronic incivility Abnormal Returns

[...] Five things we still don’t know about the flash crash.  (WashingtonPost also Macroeconomic Resilience) [...]


While the entire media circus centers around the crash, I am asking who was responsible for the resurgent buying spree? Every professional and day trader will admit that the 70% rebound in the market was "fake" and therefore a prudent trader has his finger on the sell button waiting for the collapse. I'm not sure how many traders had their finger on the buy button, or had a trade executed in their favor during those volatile 6 to 10 minutes. I would contend that the only people that got favorable executions were the very ones that instigated the tremendous decline. Finally, little has been noted that the legislation to audit the Fed and also bolster bank reforms were being discussed during the exact time of the market rout. If nothing, the experience left politicians keenly aware of what happens to the "economy" when you attempt to throttle the bankers.


well done, tough to beat a market-relevant article linking to Mauboussin, Taleb, and John Stewart!

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