Dragon Kings, Black Swans and Bubbles
April 25, 2012
"Dragon Kings" is a new term to me, and the subject on Monday evening of a presentation by Prof. Didier Sornette at an event given by PRMIA. Didier has been working on the diagnosis on financial markets bubbles, something that has been of interest to a lot of people over the past few years (see earlier post on bubble indices from RiskMinds and a follow up here).
Didier started his presentation by talking about extreme events and how many have defined different epochs in human history. He placed a worrying question mark over the European Sovereign Debt Crisis as to its place in history, and showed a pair of particularly alarming graphs of the "Perpetual Money Machine" of financial markets. One chart was a plot of savings and rate of profit for US, EU and Japan with profit rising, savings falling from about 1980 onwards, and a similar diverging one of consumption rising and wages falling in the US since 1980. Didier puts this down to finance allowing this increasing debt to occur and to perpetuate the "virtual" growth of wealth.
Corn, Obesity and Antibiotics – He put up one fascinating slide relating to positive feedback in complex systems and effectively the law of unintended consequencies. After World War II, the US Government wanted to ensure the US food supply and subsidized the production of corn. This resulted in over supply over for humans -> so the excess corn was fed to cattle -> who can't digest starch easily -> who developed e-coli infections -> which prompted the use of antibiotics in cattle -> which prompted antibiotics as growth promoters for food animals -> which resulted in cheap meat -> leading to non-sustainable meat protein consumption and under-consumption of vegetable protein. Whilst that is a lot of things to pull together, ultimately Didier suggested that the simple decision to subsidise corn had led to the current epidemic in obesity and the losing battle against bacterial infections.
Power Laws – He then touched briefly upon Power Law Distributions, which are observed in many natural phenomena (city size, earthquakes etc) and seem to explain the peaked mean and long-tails of distributions of finance far better than the traditional Lognormal distribution of traditional economic theory. (I need to catch up on some Mandelbrot I think). He explained that whilst many observations (city size for instance) fitted a power law, that the where observations that did not fit this distribution at all (in the cities example, many capital cities are much, much larger than a power law predicts). Didier then moved on to describe Black Swans, characterised as unknown unknowable events, occurring exogenously ("wrath of god" type events) and with one unique investment strategy in going long put options.
Didier said that Dragon-Kings were not Black Swans, but the major crises we have observed are "endogenous" (i.e. come from inside the system), do not conform to a power law distribution and:
- can be diagnosed in advanced
- can be quantified
- have (some) predictability
Diagnosing Bubbles – In terms of diagnosing Dragon Kings, Didier listed the following criteria that we should be aware of (later confirmed as a very useful and practical list by one of the risk managers in the panel):
- Slower recovery from perturbations
- Increasing (or decreasing) autocorrelation
- Increasing (or decreasing) cross-correlation with external driving
- Increasing variance
- Flickering and stochastic resonance
- Increased spatial coherence
- Degree of endogeneity/reflexivity
- Finite-time singularities
Didier finished his talk by describing the current work that he and ETH are doing with real and ever-larger datasets to test whether bubbles can be detected before they end, and whether the prediction of the timing of their end can be improved. So in summary, Didier's work on Dragon Kings involves the behaviour of complex systems, how the major events in these systems come from inside (e.g. the flash crash), how positive feedback and system self-configuration/organisation can produce statistical behaviour well beyond that predicted by power law distributions and certainly beyond that predicted by traditional equilibrium-based economic theory. Didier mentioned how the search for returns was producing more leverage and an ever more connected economy and financial markets system, and how this interconnectedness was unhealthy from a systemic risk point of view, particularly if overlayed by homogenous regulation forcing everyone towards the same investment and risk management approaches (see Riskminds post for some early concerns on this and more recent ideas from Baruch College)
Panel-Debate – The panel debate following was interesting. As mentioned, one of the risk managers confirmed the above statistical behaviours as useful in predicting that the markets were unstable, and that to detect such behaviours across many markets and asset classes was an early warning sign of potential crisis that could be acted upon. I thought a good point was made about the market post crash, in that the market's behaviour has changed now that many big risk takers were eliminated in the recent crash (backtesters beware!). It seems Bloomberg are also looking at some regime switching models in this area, so worth looking out for what they are up to. Another panelist was talking about the need to link the investigations across asset class and markets, and emphasised the role of leverage in crisis events. One of the quants on the panel put forward a good analogy for "endogenous" vs. "exogenous" impacts on systems (comparing Dragon King events to Black Swans), and I paraphrase this somewhat to add some drama to the end of this post, but here goes: "when a man is pushed off a cliff then how far he falls is not determined by the size of the push, it is determined by the size of the cliff he is standing on".