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resilience, not stability

Evolvability, Robustness and Resilience in Complex Adaptive Systems

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In a previous post, I asserted that “the existence of irreducible uncertainty is sufficient to justify an evolutionary approach for any social system, whether it be an organization or a macro-economy.” This is not a controversial statement – Nelson and Winter introduced their seminal work on evolutionary economics as follows: “Our evolutionary theory of economic change…is not an interpretation of economic reality as a reflection of supposedly constant “given data” but a scheme that may help an observer who is sufficiently knowledgeable regarding the facts of the present to see a little further through the mist that obscures the future.”

In microeconomics, irreducible uncertainty implies a world of bounded rationality where many heuristics become not signs of irrationality but a rational and effective tool of decision-making. But it is the implications of human action under uncertainty for macro-economic outcomes that is the focus of this blog – In previous posts (1,2) I have elaborated upon the resilience-stability tradeoff and its parallels in economics and ecology. This post focuses on another issue critical to the functioning of all complex adaptive systems: the relationship between evolvability and robustness.

Evolvability and Robustness Defined

Hiroaki Kitano defines robustness as follows: “Robustness is a property that allows a system to maintain its functions despite external and internal perturbations….A system must be robust to function in unpredictable environments using unreliable components.” Kitano makes it explicit that robustness is concerned with the maintenance of functionality rather than specific components: “Robustness is often misunderstood to mean staying unchanged regardless of stimuli or mutations, so that the structure and components of the system, and therefore the mode of operation, is unaffected. In fact, robustness is the maintenance of specific functionalities of the system against perturbations, and it often requires the system to change its mode of operation in a flexible way. In other words, robustness allows changes in the structure and components of the system owing to perturbations, but specific functions are maintained.”

Evolvability is defined as the ability of the system to generate novelty and innovate thus enabling the system to “adapt in ways that exploit new resources or allow them to persist under unprecedented environmental regime shifts” (Whitacre 2010). At first glance, evolvability and robustness appear to be incompatible: Generation of novelty involves a leap into the dark, an exploration rather than an act of “rational choice” and the search for a beneficial innovation carries with it a significant risk of failure. It’s worth noting that in social systems, this dilemma vanishes in the absence of irreducible uncertainty. If all adaptations are merely a realignment to a known systemic configuration (“known” in either a deterministic or a probabilistic sense), then an inability to adapt needs other explanations such as organisational rigidity.

Evolvability, Robustness and Resilience

Although it is typical to equate resilience with robustness, resilient complex adaptive systems also need to possess the ability to innovate and generate novelty. As Allen and Holling put it : “Novelty and innovation are required to keep existing complex systems resilient and to create new structures and dynamics following system crashes”. Evolvability also enables the system to undergo fundamental transformational change – it could be argued that such innovations are even more important in a modern capitalist economic system than they are in the biological or ecological arena. The rest of this post will focus on elaborating upon how macro-economic systems can be both robust and evolvable at the same time – the apparent conflict between evolvability and robustness arises from a fallacy of composition where macro-resilience is assumed to arise from micro-resilience, when in fact it arises from the very absence of micro-resilience.

EVOLVABILITY, ROBUSTNESS AND RESILIENCE IN MACRO-ECONOMIC SYSTEMS

The pre-eminent reference on how a macro-economic system can be both robust and evolvable at the same time is the work of Burton Klein in his books “Dynamic Economics” and “Prices, Wages and Business Cycles: A Dynamic Theory”. But as with so many other topics in evolutionary economics, no one has summarised it better than Brian Loasby: “Any economic system which is to remain viable over a long period must be able to cope with unexpected change. It must be able to revise or replace policies which have worked well. Yet this ability is problematic. Two kinds of remedy may be tried, at two different system levels. One is to try to sensitize those working within a particular research programme to its limitations and to possible alternatives, thus following Menger’s principle of creating private reserves against unknown but imaginable dangers, and thereby enhancing the capacity for internal adaptation….But reserves have costs; and it may be better , from a system-wide perspective, to accept the vulnerability of a sub-system in order to exploit its efficiency, while relying on the reserves which are the natural product of a variety of sub-systems….
Research programmes, we should recall, are imperfectly specified, and two groups starting with the same research programme are likely to become progressively differentiated by their experience, if there are no strong pressures to keep them closely aligned. The long-run equilibrium of the larger system might therefore be preserved by substitution between sub-systems as circumstances change. External selection may achieve the same overall purpose as internal adaptation – but only if the system has generated adequate variety from which the selection may be made. An obvious corollary which has been emphasised by Klein (1977) is that attempts to preserve sub-system stability may wreck the larger system. That should not be a threatening notion to economists; it also happens to be exemplified by Marshall’s conception of the long-period equilibrium of the industry as a population equilibrium, which is sustained by continued change in the membership of that population. The tendency of variation is not only a chief cause of progress; it is also an aid to stability in a changing environment (Eliasson, 1991). The homogeneity which is conducive to the attainment of conventional welfare optima is a threat to the resilience which an economy needs.”

Uncertainty can be tackled at the micro-level by maintaining reserves and slack (liquidity, retained profits) but this comes at the price of slack at the macro-level in terms of lost output and employment. Note that this is essentially a Keynesian conclusion, similar to how individually rational saving decisions can lead to collectively sub-optimal outcomes. From a systemic perspective, it is more preferable to substitute the micro-resilience with a diverse set of micro-fragilities. But how do we induce the loss of slack at firm-level? And how do we ensure that this loss of micro-resilience occurs in a sufficiently diverse manner?

The “Invisible Foot”

The concept of the “Invisible Foot” was introduced by Joseph Berliner as a counterpoint to Adam Smith’s “Invisible Hand” to explain why innovation was so hard in the centrally planned Soviet economy: “Adam Smith taught us to think of competition as an “invisible hand” that guides production into the socially desirable channels….But if Adam Smith had taken as his point of departure not the coordinating mechanism but the innovation mechanism of capitalism, he may well have designated competition not as an invisible hand but as an invisible foot. For the effect of competition is not only to motivate profit-seeking entrepreneurs to seek yet more profit but to jolt conservative enterprises into the adoption of new technology and the search for improved processes and products. From the point of view of the static efficiency of resource allocation, the evil of monopoly is that it prevents resources from flowing into those lines of production in which their social value would be greatest. But from the point of view of innovation, the evil of monopoly is that it enables producers to enjoy high rates of profit without having to undertake the exacting and risky activities associated with technological change. A world of monopolies, socialist or capitalist, would be a world with very little technological change.” To maintain an evolvable macro-economy, the invisible foot needs to be “applied vigorously to the backsides of enterprises that would otherwise have been quite content to go on producing the same products in the same ways, and at a reasonable profit, if they could only be protected from the intrusion of competition.”

Entry of New Firms and the Invisible Foot

Burton Klein’s great contribution along with other dynamic economists of the time (notably Gunnar Eliasson) was to highlight the critical importance of entry of new firms in maintaining the efficacy of the invisible foot. Klein believed that “the degree of risk taking is determined by the robustness of dynamic competition, which mainly depends on the rate of entry of new firms. If entry into an industry is fairly steady, the game is likely to have the flavour of a highly competitive sport. When some firms in an industry concentrate on making significant advances that will bear fruit within several years, others must be concerned with making their long-run profits as large as possible, if they hope to survive. But after entry has been closed for a number of years, a tightly organised oligopoly will probably emerge in which firms will endeavour to make their environments highly predictable in order to make their environments highly predictable in order to make their short-run profits as large as possible….Because of new entries, a relatively concentrated industry can remain highly dynamic. But, when entry is absent for some years, and expectations are premised on the future absence of entry, a relatively concentrated industry is likely to evolve into a tight oligopoly. In particular, when entry is long absent, managers are likely to be more and more narrowly selected; and they will probably engage in such parallel behaviour with respect to products and prices that it might seem that the entire industry is commanded by a single general!”

Again, it can’t be emphasised enough that this argument does not depend on incumbent firms leaving money on the table – on the contrary, they may redouble their attempts at static optimisation. From the perspective of each individual firm, innovation is an incredibly risky process even though the result of such dynamic competition from the perspective of the industry or macro-economy may be reasonably predictable. Of course, firms can and do mitigate this risk by various methods but this argument only claims that any single firm, however dominant cannot replicate the “risk-free” innovation dynamics of a vibrant industry in-house.

Micro-Fragility as the Hidden Hand of Macro-Resilience

In an environment free of irreducible uncertainty, evolvability suffers leading to reduced macro-resilience. “If firms could predict each others’ advances they would not have to insure themselves against uncertainty by taking risks. And no smooth progress would occur” (Klein 1977). Conversely, “because firms cannot predict each other’s discoveries, they undertake different approaches towards achieving the same goal. And because not all of the approaches will turn out to be equally successful, the pursuit of parallel paths provides the options required for smooth progress.”

The Aftermath of the Minsky Moment: A Problem of Micro-Resilience

Within the context of the current crisis, the pre-Minsky moment system was a homogeneous system with no slack which enabled the attainment of “conventional welfare optima” but at the cost of an incredibly fragile and unevolvable condition. The logical evolution of such a system post the Minsky moment is of course still a homogeneous system but with significant firm-level slack built in which is equally unsatisfactory. In such a situation, the kind of macro-economic intervention matters as much as the force of intervention. For example, in an ideal world, monetary policy aimed at reducing borrowing rates of incumbent banks and corporates will flow through into reduced borrowing rates for new firms. In a dynamically uncompetitive world, such a policy will only serve the interests of the incumbents.

The “Invisible Foot” and Employment

Vivek Wadhwa argues that startups are the main source of net job growth in the US economy and Mark Thoma links to research that confirms this thesis. Even if one disagrees with this thesis, the “invisible foot” thesis argues that if the old guard is to contribute to employment, they must be forced to give up their “slack” by the strength of dynamic competition and dynamic competition is maintained by preserving conditions that encourage entry of new firms.

MICRO-EVOLVABILITY AND MACRO-RESILIENCE IN BIOLOGY AND ECOLOGY

Note: The aim of this section is not to draw any false precise equivalences between economic resilience and ecological or biological resilience but simply to highlight the commonality of the micro-macro fallacy of composition across complex adaptive systems – a detailed comparison will hopefully be the subject of a future post. I have tried to keep the section on biological resilience as brief and simple as possible but an understanding of the genotype-phenotype distinction and neutral networks is essential to make sense of it.

Biology: Genotypic Variation and Phenotypic Robustness

In the specific context of biology, evolvability can be defined as “the capacity to generate heritable, selectable phenotypic variation. This capacity may have two components: (i) to reduce the potential lethality of mutations and (ii) to reduce the number of mutations needed to produce phenotypically novel traits” (Kirschner and Gerhart 1998). The apparent conflict between evolvability and robustness can be reconciled by distinguishing between genotypic and phenotypic robustness and evolvability. James Whitacre summarises Andrew Wagner’s work on RNA genotypes and their structure phenotypes as follows: “this conflict is unresolvable only when robustness is conferred in both the genotype and the phenotype. On the other hand, if the phenotype is robustly maintained in the presence of genetic mutations, then a number of cryptic genetic changes may be possible and their accumulation over time might expose a broad range of distinct phenotypes, e.g. by movement across a neutral network. In this way, robustness of the phenotype might actually enhance access to heritable phenotypic variation and thereby improve long-term evolvability.”

Ecology: Species-Level Variability and Functional Stability

The notion of micro-variability being consistent with and even being responsible for macro-resilience is an old one in ecology as Simon Levin and Jane Lubchenco summarise here: “That the robustness of an ensemble may rest upon the high turnover of the units that make it up is a familiar notion in community ecology. MacArthur and Wilson (1967), in their foundational work on island biogeography, contrasted the constancy and robustness of the number of species on an island with the ephemeral nature of species composition. Similarly, Tilman and colleagues (1996) found that the robustness of total yield in high-diversity assemblages arises not in spite of, but primarily because of, the high variability of individual population densities.”

The concept is also entirely consistent with the “Panarchy” thesis which views an ecosystem as a nested hierarchy of adaptive cycles: “Adaptive cycles are nested in a hierarchy across time and space which helps explain how adaptive systems can, for brief moments, generate novel recombinations that are tested during longer periods of capital accumulation and storage. These windows of experimentation open briefly, but the results do not trigger cascading instabilities of the whole because of the stabilizing nature of nested hierarchies. In essence, larger and slower components of the hierarchy provide the memory of the past and of the distant to allow recovery of smaller and faster adaptive cycles.”

Misc. Notes

1. It must be emphasised that micro-fragility is a necessary, but not a sufficient condition for an evolvable and robust macro-system. The role of not just redundancy but degeneracy is critical as is the size of the population.

2. Many commentators use resilience and robustness interchangeably. I draw a distinction primarily because my definitions of robustness and evolvability are borrowed from biology and my definition of resilience is borrowed from ecology which in my opinion defines a robust and evolvable system as a resilient one.

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Written by Ashwin Parameswaran

August 30th, 2010 at 8:38 am

14 Responses to 'Evolvability, Robustness and Resilience in Complex Adaptive Systems'

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  1. […] to the global economy. But I can’t help but draw analogies to the market in governance. Parameswaran writes: Although it is typical to equate resilience with robustness, resilient complex adaptive systems […]

  2. A very interesting site. I am surprised not to see any discussion of the Austrian tradition in economics. Hayek’s spontaneous order theory in particular and his idea of the knowledge problem and Mises’ theory of acting agents would seem to be exactly the kinds of theories for agent-based complex adaptive systems theories. Indeed, they already had many of these insights. It would not take much to adapt complexity theories to those of the Austrian economists, as both see the economy as a process.

    Troy Camplin

    10 Sep 10 at 11:16 am

  3. Troy – Thanks. I am very familiar with Hayek’s work, less so with Mises. I do mention Hayek and the Austrians reasonably often on this blog http://www.macroresilience.com/?s=hayek http://www.macroresilience.com/?s=austrian .

    Many of my posts are based on a view of human cognition that are quite consistent with Hayek’s exposition in ‘Sensory Order’ which of course is not shocking given that Hayek’s views are quite consistent with a lot of the subsequent research in the neurosciences!

    Ashwin

    10 Sep 10 at 11:41 am

  4. […] is entirely satisfactory. This post is an expansion of some thoughts I touched upon in my last post that describe the “persistent unemployment” problem as a logical consequence of a […]

  5. […] subsidy but the larger culprit is the toxic combination of Greenspan Put monetary policy and a dynamically uncompetitive cronyist financial sector. Even if the sector were more competitive it is inevitable that monetary […]

  6. […] from incumbent corporates towards households not by taxation or protectionism but by restoring the invisible foot of new firm entry. […]

  7. […] which channels does this systemic malformation occur? As I have touched upon in some earlier posts [1,2], the systemic implications of crony capitalism arise from its negative impact on new firm entry. […]

  8. Great Post, I just wanted to add that more information about robustness, evolvability, and degeneracy can be found at http://degeneracy.wordpress.com

    James Whitacre

    16 Jun 11 at 4:17 am

  9. James – Thank you! The website looks interesting. Big fan of your work.

    Ashwin

    16 Jun 11 at 7:24 am

  10. […] of other firms creating that disruptive product forces them to. An innovative economy requires an invisible kick to the ass: firms have to be forced to innovate by the threat of new competing firms entering the market. The […]

  11. […] is incompatible with macro-resilience in many complex adaptive systems as I explain here. […]

  12. […] been built not upon the positive incentive of the invisible hand but the negative incentive of the invisible foot to counter the visible hand of the control revolution. It is this threat and occasional realisation […]

  13. […] of Smithian efficiency-seeking i.e. the invisible hand, without Schumpeterian disruption i.e. the invisible foot inevitably leads to a system where capital dominates labour. Employed workers may achieve temporary […]

  14. It is the Entry of New Firms that is necessary, it is new technologies that are necessary. New firms are more likely to create and advance new technologies. But for these upstarts to survive and get investment then need property rights in their inventions – i.e. patents. The US has significantly weakened the property rights of inventors over the last decade or so. In addition, we have hamstrung their ability to raise capital – see SOX

    Dale Halling

    28 Mar 13 at 10:13 pm

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