Slow steam, fat tails and a dismal theorem

Paul Krugman's column the other day, invoking William Nordhaus's "demolition" of the forecasting model in The Limits to Growth, got me wondering about how well Nordhaus's indictment has stood up over the years. So I started poking around in the archives.

Twenty years after publication of Limits to Growth, the research team reconvened in 1992 for Beyond the Limits an  update of the earlier analysis. Nordhaus, too, followed up his earlier "blistering" review with a critique of the second version. This second review was more conciliatory, albeit still critical of the Limits to Growth and Beyond the Limits assumptions and conclusions:

While the LTG school argued that economic decline was inevitable and economists argued that the LTG argument was fallacious, the argument is ultimately an empirical matter. Put differently, critics would have gone too far had they claimed that the postulated pessimistic scenario could not hold.

Instead of simply "demolishing" the LTG model, in his second review, Nordhaus responded with his own simple model, using more a conventional generalized Cobb-Douglas production function.

Like LTG models, the general model given in the last section shows the tendency toward economic decline. In addition, there are no less than four conditions, each of which is satisfied in the LTG model, that will lead to ultimate economic stagnation, decline, or collapse...  

[However]...the entire argument can be reversed with a simple change in the specification of the model; more precisely, I will introduce technological change into the production structure and assume that the Cobb-Douglas production function accurately represents the technological possibilities for substitution.

"Ultimately, then," Nordhaus concluded his discussion of simple growth models,

...the debate about future of economic growth is an empirical one, and resolving the debate will require analysts to examine fundamental structural parameters of the economy... How large are the drags from natural resources and land? What is the quantitative relationship between technological change and the resource-land drag? How does human population growth behave as incomes rise? How much substitution is possible between labor and capital on the one hand, and scarce natural resources, land, and pollution abatement on the other? These are empirical questions that cannot be settled solely by theorizing.

One of the discussants for Nordhaus's 1992 Brookings paper was Martin Weitzman, who described it as "an outstanding paper." that "represents the economic state of the art, circa 1992, in dealing seriously and honestly with the major limits-to-growth arguments." One could almost imagine hearing the scalpel being quietly honed as Weitzman administered that subtle anesthesia.

Fast forward another two decades and it is Nordhaus's turn to comment on a paper by Weitzman, "On modeling and interpreting the economics of catastrophic climate change."

In an important paper, Weitzman (2009) has proposed what he calls a dismal theorem. He summarizes the theorem as follows: "[T]he catastrophe-insurance aspect of such a fat-tailed unlimited-exposure situation, which can never be fully learned away, can dominate the social-discounting aspect, the pure-risk aspect, and the consumption-smoothing aspect." The general idea is that under limited conditions concerning the structure of uncertainty and societal preferences, the expected loss from certain risks such as climate change is infinite and that standard economic analysis cannot be applied.

Nordhaus concluded his discussion of Weitzman's theorem on a somber and humble note:

In many cases, the data speak softly or not at all about the likelihood of extreme events. This means that reasonable people may have quite different views about the likelihood of extreme events, such as the catastrophic outcomes of climate change, and that there are no data to adjudicate such disputes. This humbling thought applies more broadly, however, as there are indeed deep uncertainties about virtually every issue that humanity faces, and the only way these uncertainties can be resolved is through continued careful consideration and analysis of all data and theories.

The word "growth" doesn't appear in Nordhaus's 16-page commentary. Pascal's wager, anyone?

Krugman, straw man, beggar, thief

In his "Slow Steaming..." column today, Paul Krugman blatantly misrepresented and trivialized Mark Buchanan's argument:

Buchanan says that it’s not possible to have something bigger — which is apparently what he thinks economic growth has to mean — without using more energy.

Wrong. Buchanan said bigger things, as a rule, use more energy. He also said that efficiencies of scale don't overturn that rule. He referred to data about economic growth and energy use, not "what he thinks economic growth has to mean":

Data from more than 200 nations from 1980 to 2003 fit a consistent pattern: On average, energy use increases about 70 percent every time economic output doubles. This is consistent with other things we know from biology. Bigger organisms as a rule use energy more efficiently than small ones do, yet they use more energy overall. The same goes for cities. Efficiencies of scale are never powerful enough to make bigger things use less energy.

Krugman disparaged Buchanan for reprising the claims and title of the book that William Nordhaus "demolished so effectively forty years ago":

...not only does he make the usual blithe claims about what economists never think about; even his title is almost exactly the same as the classic (in the sense of classically foolish) Jay Forrester book that my old mentor, Bill Nordhaus, demolished so effectively forty years ago.

I'll leave it to posterity whether or not Nordhaus "demolished" Limits to Growth. Forty years on, Brian Hayes wrote a less "blistering" critique, published in American Scientist, judging Forrester's mathematical model to be "more of a polemical tool than a scientific instrument" but concluding the book's message of limits is worth listening to. Defenders of the book have argued that Nordhaus misunderstood or misrepresented the structure of the model and whether or not the model used historical data (it did) -- the title of Nordhaus's review was "World dynamics: measurement without data."

But, following the Krugman's link to his earlier article reveals that the "foolishness" or otherwise of the book Nordhaus supposedly demolished is really beside the point. Krugman's conclusion in that earlier article directly contradicts the Pollyanna claims he is now making:

You might say that this is my answer to those who cheerfully assert that human ingenuity and technological progress will solve all our problems. For the last 35 years, progress on energy technologies has consistently fallen below expectations. 

...

But anyway, while the Limits to Growth stuff of the 1970s was a mess, the history of energy technology doesn’t support extreme optimism, either.

You've really got to follow the links.

Paul Krugman’s Errors and Omissions

Richard Heinberg of the Post Carbon Institute replies to Paul Krugman's "Errors and Emissions" Op-ed.

Four More Planets!

"In theory GDP growth could continue indefinitely – if it weren't linked to something real."

William Rees, who along with Mathis Wackernagel developed Ecological Footprint analysis, commented on Paul Krugman's flippant slur on "degrowth" as an odd bedfellow of "the prophets of climate despair." The bottom line for Rees is that it is not really a choice between growth or degrowth but between planned, orderly degrowth or painful, chaotic degrowth imposed by nature. Growth in GDP could, "in theory," go on indefinitely ONLY if it wasn't linked to the biophysical world, which historically and currently it is. With permission, I reproduce Bill's comments below:

One might like to think that 'de-growth' is a non-issue – that somehow the human enterprise can continue to expand – but this is not a realistic proposition. De-growth will happen probably in the next few decades; the relevant question is ‘by what means?’ 

Here’s why: 

First, any analysis of this type should be based on available data, not mere assertion of preferences or beliefs. "Show me the numbers" is the first commandment of sustainability assessment. 

Second, we should clarify what we are talking about and what we are not talking about. Here I am not talking about increases/decreases in income or GDP per se. Income growth or GDP/growth per capita is a money measure with no physical dimensions. Money is mere abstraction – in fact, most money today is mere 'number money' or electronic money that exists only in computers and whether the number is $1 or $1,000,000,000 makes no difference to the planet whatsoever. In theory, then, GDP growth could continue indefinitely – if it weren't linked to something real. 

But it is linked to something real, the biophysical world. People buy real wealth (food, clothing, shelter, autos, electronic toys, etc.) with money wealth and there has never been a period when increases in money income were not accompanied by increases in real energy and material consumption. At higher income levels the relationship begins to level out because of greater ‘factor productivity’ (efficiency) and as more discretionary income goes to purchasing services (economists call this ‘decoupling’), but: a) decoupling is, so far, a marginal trend even in rich countries and; b) most of the world’s people have not nearly satisfied their material needs, let alone wants. Consequently, global material and energy throughput is generally increasing in both per capita and gross terms. Remember too that, from a biophysical perspective, all economic production is mostly consumption—a vastly larger quantity of available energy/matter is processed or consumed than is contained in the products produced (and the ratio is deteriorating because of diminishing returns)

And herein lies the problem. Energy and material production and consumption has material consequences for ecosystems that are vital for sustainability, i.e., survival. Consider just one fact: all food and fibre flows through the economy are produced by ecosystems and all the wastes of both our bio-metabolism and industrial metabolism must be assimilated and neutralized by ecosystems.

These are measurable processes with measurable consequences. Ecological footprint analysis shows that to produce the bio-resources consumed, and to assimilate just the carbon wastes of the average European requires about five hectares of ecosystems of global average productivity (5 gha). Typical North Americans use the ecological services of 7-8 gha/capita. Meanwhile, people in the most impoverished African countries get by on the life support of perhaps half a gha. (As I said, there is a clear positive relationship between income and the consumption of ‘nature’.) By the way, these are underestimates because we use the more optimistic data where there are conflicts between sources, not all material/waste flows are included and because we assume sustainable land and water use which it is not the case.

The problem is that there are only 12 to 13 billion hectares of land and water ecosystems productive enough to support economic activity on Earth. That’s about 1.7 gha per capita (at the present population of 7.2 billion). This means that Europeans are using three times and North Americans five times their ‘fair Earthshares’. Put another way, we’d need several more Earth-like planets to support just the present world population at European or North American material standards with current technologies. (Poor people don’t get nearly their fair Earthshare because they don’t have enough money to compete in the marketplace.)

Now, the average human ecological footprint is about 2.7 gha so even at today’s average levels of material consumption, the human enterprise is in overshoot by about 50%. This means humans are consuming faster than ecosystems can regenerate and producing waste faster than ecosystems can assimilate. (Climate change is driven, in part, by carbon dioxide emissions. CO2 is the largest waste by weight of industrial economies so, in this sense, climate change is a waste-management problem.) Economic growth and accompanying increases in energy and material consumption today are based, in part, on the depletion of so-called ‘natural capital’ and on filling waste sinks to over-flowing. The continuation and expansion of these trends will precipitate significant changes in, or even the collapse of biophysical systems, including the climate system. Dependent human economies and societies will not be far behind (this constitutes unplanned de-growth).

This is not fantasy. Eco-failure is already happening regionally and, without global agreements leading to major reductions in human energy and material demand (i.e., planned de-growth), will happen globally. Indeed, globalization and trade ensure that that the next collapse will be global—many densely populated high-income countries have long since overshot their domestic carrying capacities and would long ago have collapsed without access to the resources/sinks of less developed regions. Globalization blinds citizens of nations in overshoot to the perils of over-population and over-consumption, since it eliminates any direct ‘negative feedback’ from their having exceeded national limits. (Japan, for example, despite its recent economic stall, still uses 5-7 times its domestic biocapacity, so far with impunity.) Keep in mind that that, absent access to distant sources, the destructive over-exploitation of regional ecosystems contributed to the collapse of many previous civilizations on all continents from Sumer to the Maya.

Summary and bottom line:

Historic and contemporary evidence suggests that global de-growth (meaning significant reductions in aggregate and per capita energy and material consumption and in the human population) is inevitable. If it is imposed by nature, it could be painful and chaotic; but a planned contraction of the human enterprise (both population and per capita consumption) to a sustainable steady-state could be relatively smooth and orderly. The plan might require accelerated de-growth in high-income consumer countries to accommodate greater consumption in poor regions for the sake of greater material equality.

Which form of de-growth would you prefer?

Which is the more likely to occur?

PS: Eco-footprint analysis is based on real data from the most reliable sources available for ecosystems productivity and for national production, consumption, and material trade. Some people do not like the results of such analyses, particularly the documentation of over-shoot and the support this provides for the notion of biophysical limits to growth and the need for material de-growth. Fair enough, but those who reject the findings on these grounds have an obligation to provide an alternative explanation and solution. The questions are: How can the human enterprise, as a fully-contained, dependent growing sub-system of the finite non-growing ecosphere (tip o' the hat to Herman Daly), continue to expand indefinitely? Once in severe overshoot, is a sustainable recovery possible without significant material de-growth?

André Orléan on the Legitimacy Crisis in Economics

From the Introduction to The Empire of Value (2014)

The economics profession is presently experiencing a grave crisis of legitimacy. There was a time when it sought to provide sound guidance for democratic societies by improving the effectiveness of reasoned public policy. But now, through its own negligence, it has shown itself to be a source of confusion and error. It allowed a suicidal scheme of financial deregulation to be put into effect, without any prior attempt having been made to assess the scope of the risks involved or to devise appropriate precautions against them. Instead of awakening minds, economics has put them to sleep; instead of enlightening them, it has cast them into darkness. The disrepute in which the profession is held today stands in proportion to its own failure, which is extreme and without precedent. 

The reaction of economists to the scathing criticism that has been directed at them is striking above all for its lack of intellectual courage. Even if a majority is prepared to admit that very harmful mistakes have been made, most economists also persist in warning against throwing out the baby with the bathwater. To be sure, they say, undue reliance on a type of modeling that recklessly overrates the virtues of competition, together with a dogmatic insistence on the hyperrationality of economic actors, is indefensible. But these shortcomings give a distorted picture of the discipline. Economics is perfectly capable of correcting its excesses, by drawing upon new fields of research such as multiple equilibrium theory and experimental economics, even neuro-economics. So say the economists. And yet instruction at the university level remains the same as it was before the crisis; research likewise proceeds on the same assumptions as before, using the same methods as before. However many newspapers and magazines announce the return of Marx, Schumpeter, and Keynes, the fact of the matter is that nothing has really changed. 

None of this should come as a surprise. Science obeys its own rhythms. Economists are not like weathervanes, pointing this way or that with every shift in the winds; they cannot be expected today to teach the opposite of what they professed yesterday. Nor is economic theory a mere collection of recipes that can be sampled in response to changing tastes; it is a highly structured body of propositions built up from falsifiable hypotheses, rigorous methods of proof, and a vast archive of established results—what the historian and philosopher of science Thomas Kuhn famously called a paradigm. Kuhn showed that it is in the very nature of paradigmatic inquiry to resist challenges to its view of the world. For a paradigm to be overturned at a moment of crisis, not only must a persistent series of anomalies have been observed, in contradiction of the accepted wisdom, but, no less importantly, there must be a new paradigm ready to take the place of the old one. Now, the fact that an economic crisis brings previously unsuspected problems to light does not mean that fresh solutions are available on demand. It is true that economists today quote Keynes, Minsky, and Kindleberger more often than they used to. But this ought not fool anyone. No matter that economists now find it convenient to distance themselves from the neoclassical assumption of efficient financial markets, the theoretical framework that organizes their thinking and their teaching remains unchanged. It has been kept in place exactly as it was. 

The present work proposes to make a new beginning. It proceeds from the conviction that the difficulties encountered by economic theory owe nothing to momentary circumstances, but are the consequence of a fundamentally mistaken conception of economic behavior.

“The economics profession is presently experiencing a grave crisis of legitimacy.”

I've just started reading The Empire of Value by André Orléan and I am very impressed. As was Jamie Galbraith in his blurb for the book:

“In lucid, accessible language, André Orléan resurrects and explores the vital (but neglected) problem of value, grappling along the way with some fundamental defects of conventional theory. Through his mimetic hypothesis, the role of money emerges in the central role that both classical political economy and neoclassical economics denied to it. The Empire of Value is a bold argument, and a deep rejection of the justification for reliance on markets, except as a device for obtaining consent.”

First sentence in the introduction to Empire of Value: “The economics profession is presently experiencing a grave crisis of legitimacy.” This proves to be understatement, not hyperbole.