Complexity, Problem Solving, and Sustainable Societies by Joseph Tainter

“Historical knowledge is essential to practical applications of ecological economics. Systems of problem solving develop greater complexity and higher costs over long periods. In time such systems either require increasing energy subsidies or they collapse. Diminishing returns to complexity in problem solving limited the abilities of earlier societies to respond sustainably to challenges, and will shape contemporary responses to global change. To confront this dilemma we must understand both the role of energy in sustaining problem solving, and our historical position in systems of increasing complexity.”


“To design policies for today and the future we need to understand social and economic processes at all temporal scales, and comprehend where we are in historical patterns . . . . One might expect that in a rational, problem-solving society, we would eagerly seek to understand historical experiences. In actuality, our approaches to education and our impatience for innovation have made us averse to historical knowledge. In ignorance, policy makers tend to look for the causes of events only in the recent past. As a result, while we have a greater opportunity than the people of any previous era to understand the long-term reasons for our problems, that opportunity is largely ignored. Not only do we not know where we are in history, most of our citizens and policy makers are not aware that we ought to.”

“. . . . our approach to resolving our problems has been to develop the most complex society and economy of human history, it is important to understand how previous societies fared when they pursued analogous strategies . . . . part of our response to global change must be to understand the long-term evolution of problem-solving systems.”


Complexity is generally understood to refer to such things as the size of a society, the number and distinctiveness of its parts, the variety of specialized social roles that it incorporates, the number of distinct social personalities present, and the variety of mechanisms for organizing these into a coherent, functioning whole. Augmenting any of these dimensions increases the complexity of a society. Hunter-gatherer societies (by way of illustrating one contrast in complexity) contain no more than a few dozen distinct social personalities, while modern European censuses recognize 10,000 to 20,000 unique occupational roles, and industrial societies may contain overall more than 1,000,000 different kinds of social personalities.”

“A society that is more complex has more sub-groups and social roles, more networks among groups and individuals, more horizontal and vertical controls, higher flow of information, greater centralization of information, more specialization, and greater interdependence of parts. Increasing any of these dimensions requires biological, mechanical, or chemical energy. In the days before fossil fuel subsidies, increasing the complexity of a society usually meant that the majority of its population had to work harder.”

The reason why complexity increases is that, most of the time, it works. Complexity is a problem solving strategy that emerges under conditions of compelling need or perceived benefit. Throughout history, the stresses and challenges that human populations have faced (in foraging and agriculture, technology, competition, warfare, and arms races, sociopolitical control and specialization, research and development)have often been resolved by becoming more complex. In each of these areas, complexity increases through greater differentiation, specialization, and integration. The history of cultural complexity is the history of human problem solving.”

Complexity can be both beneficial and detrimental. Its destructive potential is evident in historical cases where increased expenditures on socioeconomic complexity reached diminishing returns, and ultimately, in some instances, negative returns. This outcome emerges from the normal economic process: simple, inexpensive solutions are adopted before more complex, expensive ones.

Thus, as human populations have increased, hunting and gathering has given way to increasingly intensive agriculture, and to industrialized food production that consumes more energy than it produces. Minerals and energy production move consistently from easily accessible, inexpensively exploited reserves to ones that are costlier to find, extract, process, and distribute. Socioeconomic organization has evolved from egalitarian reciprocity, short-term leadership, and generalized roles to complex hierarchies with increasing specialization.

As a society increases in complexity, it expands investment in such things as resource production, information processing, administration, and defense. The benefit/cost curve for these expenditures may at first increase favorably, as the most simple, general, and inexpensive solutions are adopted (a phase not shown on this chart). Yet as a society encounters new stresses, and inexpensive solutions no longer suffice, its evolution proceeds in a more costly direction. Ultimately a growing society reaches a point where continued investment in complexity yields higher returns, but at a declining marginal rate . . . . Two things make a society liable to collapse at this point:

  1. First new emergencies impinge on a people who are investing in a strategy that yields less and less marginal return. As such a society becomes economically weakened it has fewer reserves with which to counter major adversities. A crisis that the society might have survived in its earlier days now becomes insurmountable.
  2. Diminishing returns make complexity less attractive and breed disaffection. The so-called “complexity of modern life” is a regular complaint in popular discourse. Some of the public discontent with government stems from the fact that government adds complexity to people’s lives. As taxes and other costs rise and there are fewer benefits at the local level, more and more people are attracted by the idea of being independent. The society “decomposes” as people pursue their immediate needs rather than the long-term goals of the leadership.

To illustrate these conditions it is useful to review three examples of increasing complexity and costliness in problem solving: the collapse of the Roman Empire, the development of industrialism, and trends in contemporary science.

The Collapse of The Roman Empire

The Roman Empire provides history’s best-documented example of how increasing complexity to resolve problems leads to higher costs, diminishing returns, alienation of a support population, economic weakness, and collapse.

In the third century A.D. constant crises forced the emperors to double the size of the army and increase both the size and complexity of the government. To pay for this, masses of worthless coins were produced, supplies were commandeered from peasants, and the level of taxation was made even more oppressive (up to two-thirds of the net yield after payment of rent). Inflation devastated the economy. Lands and population were surveyed across the empire and assessed for taxes. Communities were held corporately liable for any unpaid amounts. While peasants went hungry or sold their children into slavery, massive fortifications were built, the size of the bureaucracy doubled, provincial administration was made more complex, large subsidies in gold were paid to Germanic tribes, and new imperial cities and courts were established.

With rising taxes, marginal lands were abandoned and population declined. Peasants could no longer support large families. To avoid oppressive civic obligations, the wealthy fled from cities to establish self-sufficient rural estates. Ultimately, to escape taxation, peasants voluntarily entered into feudal relationships with these land holders. A few wealthy families came to own much of the land in the western empire, and were able to defy the imperial government. The empire came to sustain itself by consuming its capital resources; producing lands and peasant population.

In the end it could no longer afford to solve the problems of its own existence.

Population, Resources, and Industrialism

It is useful to discuss a historical case that turned out quite differently for increasingly complex society. In one of the most interesting works of economic history, Richard Wilkinson (1973) showed that in late-and post-medieval England, population growth and deforestation stimulated economic development, and were at least partly responsible for the Industrial Revolution.

Major increases in population, at around 1300, 1600, and in the late 18th century, led to intensification in agriculture and industry. As forests were cut to provide agricultural land and fuel for a growing population, England’s heating, cooking, and manufacturing needs could no longer be met by burning wood. Coal came to be increasingly important, although it was adopted reluctantly. Coal was costlier to obtain and distribute than wood, and restricted in its occurrence. It required a new, costly distribution system. As coal gained importance in the economy the most accessible deposits were depleted. Mines had to be sunk ever deeper, until groundwater came to be a problem. Ultimately, the steam engine was developed and put to use pumping water from mines.

With the development of a coal-based economy, a distribution system, and the steam engine, several of the most important technical elements of the Industrial Revolution were in place. Industrialism, that great generator of economic well-being, came in part from steps to counteract the consequences of resource depletion, supposedly a generator of poverty and collapse. Yet it was a system of increasing complexity that did not take long to show diminishing returns in some sectors. This point will be raised again later.

Science and Problem Solving

Contemporary science is humanity’s greatest exercise in problem solving.

Science is an institutional aspect of society, and research is an activity that we like to think has a high return. Yet as generalized knowledge is established early in the history of a discipline, the work that remains to be done is increasingly specialized. These types of problems tend to be increasingly costly and difficult to resolve, and on average advance knowledge only by small increments.

“. . . with every advance the difficulty of the task is increased”. As easier questions are resolved, science moves inevitably to more complex research areas and to larger, costlier organizations. Rescher suggests that “As science progresses within any of its specialized branches, there is a marked increase in the overall resource-cost to realizing scientific findings of a given level [of] intrinsic significance . . .”

Once all of the findings at a given state-of-the-art level of investigative technology have been realized, one must move to a more expensive level . . . . In natural science we are involved in a technological arms race: with every victory over nature the difficulty of achieving the breakthroughs which lie ahead is increased . . . . Increasing investments in research yield declining marginal returns.

Implications of the Examples

The Roman Empire, industrialism, and science are important, not only for their own merits, but also because they exemplify: (1) how problem solving evolves along a path of increasing complexity, higher costs, and declining marginal returns (Tainter 1988), and (2) some different outcomes of that process. In the next section, I discuss what these patterns imply for our efforts to address contemporary problems.



This historical discussion gives a perspective on what it means to be practical and sustainable.

The experience of the Roman Empire is again instructive. Most actions that the Roman government took in response to crises-such as debasing the currency, raising taxes, expanding the army, and conscripting labor-were practical solutions to immediate problems. It would have been unthinkable not to adopt such measures. Cumulatively, however, these practical steps made the empire ever weaker, as the capital stock (agricultural land and peasants) was depleted through taxation and conscription. Over time, devising practical solutions drove the Roman Empire into diminishing, then negative, returns to complexity.

The implication is that to focus a problem-solving system, such as ecological economics, on practical applications will not automatically increase its value to society, nor enhance sustainability. The historical development of problem-solving systems needs to be understood and taken into consideration.

Most who study contemporary issues certainly would agree that solving environmental and economic problems requires both knowledge and education. A major part of our response to current problems has been to increase our level of research into environmental matters, including global change. As our knowledge increases and practical solutions emerge, governments will implement solutions and bureaucracies will enforce them. New technologies will be developed. Each of these steps will appear to be a practical solution to a specific problem. Yet cumulatively these practical steps are likely to bring increased complexity, higher costs, and diminishing returns to problem solving.’ Richard Norgaard has stated the problem well: “Assuring sustainability by extending the modem agenda … will require, by several orders of magnitude, more data collection, interpretation, planning, political decision-making, and bureaucratic control (e.g. to reduce sulfur dioxide in the air of a U.S. city by 9.6 times, or particulates by 3.1 times, raises the cost of pollution control by 520 times).”

Bureaucratic regulation itself generates further complexity and costs. As regulations are issued and taxes established, those who are regulated or taxed seek loopholes and lawmakers strive to close these. A competitive spiral of loophole discovery and closure unfolds, with complexity continuously increasing. In these days when the cost of government lacks political support, such a strategy is unsustainable. It is often suggested that environmentally benign behavior should be elicited through taxation incentives rather than through regulations. While this approach has some advantages, it does not address the problem of complexity, and may not reduce overall regulatory costs as much as is thought. Those costs may only be shifted to the taxation authorities, and to the society as a whole.

It is not that research, education, regulation, and new technologies cannot potentially alleviate our problems. With enough investment perhaps they can. The difficulty is that these investments will be costly, and may require an increasing share of each nation’s gross domestic product. With diminishing returns to problem solving, addressing environmental issues in our conventional way means that more resources will have to be allocated to science, engineering, and government. In the absence of high economic growth this would require at least a temporary decline in the standard of living, as people would have comparatively less to spend on food, housing, clothing, medical care, transportation, and entertainment.

To circumvent costliness in problem solving it is often suggested that we use resources more intelligently and efficiently. Timothy Allen and Thomas Hoekstra, for example, have suggested that in managing ecosystems for sustainability, managers should identify what is missing from natural regulatory process and provide only that. The ecosystem will do the rest (this will be the economic strategy of Natural Capitalism). Let the ecosystem (i.e., solar energy) subsidize the management effort rather than the other way around. It is an intelligent suggestion. At the same time, to implement it would require much knowledge that we do not now possess. That means we need research that is complex and costly, and requires fossil-fuel subsidies.

Lowering the costs of complexity in one sphere causes them to rise in another.

Agricultural pest control illustrates this dilemma. As the spraying of pesticides exacted higher costs and yielded fewer benefits, integrated pest management was developed. This system relies on biological knowledge to reduce the need for chemicals, and employs monitoring of pest populations, use of biological controls, judicious application of chemicals, and careful selection of crop types and planting dates. It is an approach that requires both esoteric research by scientists and careful monitoring by farmers. Integrated pest management violates the principle of complexity aversion, which may partly explain why it is not more widely used.

Such issues help to clarify what constitutes a sustainable society. The fact that problem-solving systems seem to evolve to greater complexity, higher costs, and diminishing returns has significant implications for sustainability. In time, systems that develop in this way are either cut off from further finances, fail to solve problems, collapse, or come to require large energy subsidies. This has been the pattern historically in such cases as the Roman Empire, the Lowland Classic Maya, Chacoan Society of the American Southwest, warfare in Medieval and Renaissance Europe, and some aspects of contemporary problem solving. These historical patterns suggest that one of the characteristics of a sustainable society will be that it has a sustainable system of problem solving-one with increasing or stable returns, or diminishing returns that can be financed with energy subsidies of assured supply, cost, and quality.

Industrialism illustrates this point. It generated its own problems of complexity and costliness. These included railways and canals to distribute coal and manufactured goods, the development of an economy increasingly based on money and wages, and the development of new technologies. While such elements of complexity are usually thought to facilitate economic growth, in fact they can do so only when subsidized by energy. Some of the new technologies, such as the steam engine, showed diminishing returns to innovation quite early in their development. What set industrialism apart from all of the previous history of our species was its reliance on abundant, concentrated, high-quality energy. With subsidies of inexpensive fossil fuels, for a long time many consequences of industrialism effectively did not matter. Industrial societies could afford them. Fossil fuels made industrialism, and all that flowed from it (such as science, transportation, medicine, employment, consumerism, high-technology war, and contemporary political organization), a system of problem solving that was sustainable for several generations.

Energy has always been the basis of cultural complexity and it always will be.

If our efforts to understand and resolve such matters as global change involve increasing political, technological, economic, and scientific complexity, as it seems they will, then the availability of energy per capita will be a constraining factor. To increase complexity on the basis of static or declining energy supplies would require lowering the standard of living throughout the world. In the absence of a clear crisis very few people would support this. To maintain political support for our current and future investments in complexity thus requires an increase in the effective per capita supply of energy-either by increasing the physical availability of energy, or by technical, political, or economic innovations that lower the energy cost of our standard of living.


This [paper] on the past clarifies potential paths to the future.

One often-discussed path is cultural and economic simplicity and lower energy costs. This could come about through the “crash” that many fear-a genuine collapse over a period of one or two generations, with much violence, starvation, and loss of population. The alternative is the “soft landing” that many people hope for-a voluntary change to solar energy and green fuels, energy-conserving technologies, and less overall consumption. This is a utopian alternative that, as suggested above, will come about only if severe, prolonged hardship in industrial nations makes it attractive, and if economic growth and consumerism can be removed from the realm of ideology.

The more likely option is a future of greater investments in problem solving, increasing overall complexity, and greater use of energy. This option is driven by the material comforts it provides, by vested interests, by lack of alternatives, and by our conviction that it is good. If the trajectory of problem solving that humanity has followed for much of the last 12,000 years should continue, it is the path that we are likely to take in the near future.

One point should be clear. It is essential to know where we are in history. We have the the opportunity to become the first people in history to understand how a society’s problem-solving abilities change. To know that this is possible yet not to act upon it would be a great failure of the practical application of ecological economics.

Complexity, Problem Solving, and Sustainable Societies by Joseph Tainter at

Keywords : ecosocial crisis, complexity, complex systems, evolution, bureaucracy, government, democracy, political economy, problem solving, sustainability, economic growth, industrialism, consumerism, energy, cheap oil, peak oil, appropriate science and technology, voluntary simplicity
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