Back in December 1968, an ecologist and microbiologist named Garrett Hardin published a short essay called "The Tragedy of the Commons" in Science (December 13, 1968, pp. 1243-1248). The phrase "tragedy of the commons" passed into everyday use, and the article itself spawned a vast research literature. Fifty years later, what's it all about?
Here is how Hardin conceptualised the tragedy of the commons:
"The tragedy of the commons develops in this way. Picture a pasture open to all. It is to be expected that each herdsman will try to keep as many cattle as possible on the commons. Such an arrangement may work reasonably satisfactorily for centuries because tribal wars, poaching, and disease keep the numbers of both man and beast well below the carrying capacity of the land. Finally, however, comes the day of reckoning, that is, the day when the long-desired goal of social stability becomes a reality. At this point, the inherent logic of the commons remorselessly generates tragedy.
As a rational being, each herdsman seeks to maximise his gain. Explicitly or implicitly, more or less consciously, he asks, "What is the utility to me of adding one more animal to my herd?" This utility has one negative and one positive component.
1) The positive component is a function of the increment of one animal. Since the herdsman receives all the proceeds from the sale of the additional animal, the positive utility is nearly +1.
2) The negative component is a function of the additional overgrazing created by one more animal. Since, however, the effects of overgrazing are shared by all the herdsmen, the negative utility for any particular decision-making herdsman is only a fraction of -1.
Adding together the component partial utilities, the rational herdsman concludes that the only sensible course for him to pursue is to add another animal to his herd. And another; and another.... But this is the conclusion reached by each and every rational herdsman sharing a commons. Therein is the tragedy. Each man is locked into a system that compels him to increase his herd without limit--in a world that is limited. Ruin is the destination toward which all men rush, each pursuing his own best interest in a society that believes in the freedom of the commons. Freedom in a commons brings ruin to all."
Hardin applied this concept in a variety of contexts. For example, he points out that free parking in shopping areas is a kind of commons; that national parks are a kind of commons; that emitting pollution into air and water diminishes the common environment. But the main focus of his essay is on human overpopulation. Hardin wrote:
"Perhaps the simplest summary of this analysis of man's population problems is this: the commons, if justifiable at all, is justifiable only under conditions of low-population density. As the human population has increased, the commons has had to be abandoned in one aspect after another. First we abandoned the commons in food gathering, enclosing farm land and restricting pastures and hunting and fishing areas. These restrictions are still not complete throughout the world. Somewhat later we saw that the commons as a place for waste disposal would also have to be abandoned. Restrictions on the disposal of domestic sewage are widely accepted in the Western world; we are still struggling to close the commons to pollution by automobiles, factories, insecticide sprayers, fertilising operations, and atomic energy installations. ...
Every new enclosure of the commons involves the infringement of somebody's personal liberty. ... The most important aspect of necessity that we must now recognise, is the necessity of abandoning the commons in breeding. No technical solution can rescue us from the misery of overpopulation. Freedom to breed will bring ruin to all. At the moment, to avoid hard decisions many of us are tempted to propagandise for conscience and responsible parenthood. The temptation must be resisted, because an appeal to independently acting consciences selects for the disappearance of all conscience in the long run, and an increase in anxiety in the short. The only way we can preserve and nurture other and more precious freedoms is by relinquishing the freedom to breed, and that very soon."
Hardin did not go into detail about population policy here, but in general, he writes approvingly of "mutual coercion, mutually agreed upon by the majority of the people affected."
Over time, the application of the tragedy of the commons to human population is less common. Back in the late 1960s and early 1970s, it was fairly common to hear predictions that human overpopulation would within a decade or two lead to mass starvation. For example, Paul Ehrlich's 1968 best-selling book The Population Bomb started with "The battle to feed all of humanity is over” and then moved on to comments like "hundreds of millions of people are going to starve to death” and “nothing can prevent a substantial increase in the world death rate.” But although human population has continued to grow, birth rates have also fallen substantially and life expectancies have grown. There has been a remarkable decline in global poverty in the last few decades. For the world as a whole, more people are obese than malnourished. Even where global poverty remains, we are now more likely in 2018 to perceive it as a problem of too little economic development, rather than a problem of too many people.
Another shift in how we think about the tragedy of the commons 50 years later is that Hardin seems to argue that there are really only two choices for a commons: ending the commons and turning it over to private ownership, or government control. But the menu of choices turns out to be broader. For example, government control applied to issues of environmental pollution can include both command-and-control regulation, but also other possibilities like pollution taxes and tradable pollution permits.
In addition, a powerful body of research, led by the work of Elinor Ostrom (Nobel '09) showed that a local commons could in many cases be managed by groups, without either government ownership or privatisation. Thirty years after Hardin's essay,
Ostrom along with co-authors Joanna Burger, Christopher B. Field, Richard B. Norgaard, and David Policansky discussed this view in "Revisiting the Commons: Local Lessons, Global Challenges," published in Science (April 9, 1999). As one of many examples where group management of a commons turned out perhaps unexpectedly well, they wrote:
Although tragedies have undoubtedly occurred, it is also obvious that for thousands of years people have self-organised to manage common-pool resources, and users often do devise long-term, sustainable institutions for governing these resources. .... Both government ownership and privatisation are themselves subject to failure in some instances. For example, Sneath shows great differences in grassland degradation under a traditional, self-organised group-property regime versus central government management. A satellite image of northern China, Mongolia, and southern Siberia shows marked degradation in the Russian part of the image, whereas the Mongolian half of the image shows much less degradation. In this instance, Mongolia has allowed pastoralists to continue their traditional group-property institutions, which involve large-scale movements between seasonal pastures, while both Russia and China have imposed state-owned agricultural collectives that involve permanent settlements. More recently, the Chinese solution has involved privatization by dividing the “pasture land into individual allocations for each herding household”. About three-quarters of the pasture land in the Russian section of this ecological zone has been degraded and more than one-third of the Chinese section has been degraded, while only one-tenth of the Mongolian section has suffered equivalent loss. Here, socialism and privatization are both associated with more degradation than resulted from a traditional group-property regime.
Ostrom and others tried to look at what they called "social-ecological systems" in fine-grained and pragmatic detail, steering away from grand pronouncements about what worked, and instead trying to sort out why group property rights worked in specific settings, but not others.
The 50th anniversary of the "tragedy of the commons" essay has brought some ruminations. Science magazine, the original publisher of Hardin's essay, marked the occasion with a suite of short comments in the December 14 issue. Some of the comments emphasise Ostrom-style arguments: how a wide range of society's over time have developed a set of moral beliefs and cultural practices that can sometimes support cooperation over large-scale irrigation projects and resource management. But such arrangements are not inevitable, and it's not clear how to build them where they do not already exist.
Matthew O. Jackson mentions one key issue, which is that even when there are overall social gains from some form of social cooperation, benefits and costs may not be evenly distributed--and some can even experience outright losses. In the context of climate change and the global commons, he writes:
"Over the past five decades, we have come to a deep understanding of commons problems and how to solve them: They are not zero-sum games, but instead offer substantial gains from cooperation. Game theory and market design have helped us understand how to provide appropriate incentives. For instance, taxes as well as cap-and-trade systems can be designed to make the price of emitting carbon include its ultimate social/climate cost, and subsidies can make the prices of alternative technologies reflect their ultimate social benefit. However, a challenge with global commons problems is that solving the incentive problems often leads the collective gains to be distributed very unevenly; the costs can even outweigh the benefits for some parties. There are many players with enormous differences in wealth and interests around the planet—both within and across countries—facing different consequences from commons problems and abilities to pay for them. Yet, universal cooperation is needed, including coordinated limits and the willingness and the ability to enforce those limits. Thus, the main challenges that we face are political."
Brett M. Frischmann, Michael J. Madison, Katherine J. Strandburg offer a different angle, applying the tragedy of the commons to a build-up of knowledge in society:
Intellectual resources have their own tragedy-of-the-commons allegory. Replace Hardin's pasture with an idea, and consider what happens when the resource, the idea, is openly accessible to all. ... Avoiding cultural, technological, and scientific stagnation thus seems to require collective action to ensure adequate investment in knowledge creation. To facilitate this, many analysts assume two options: government subsidies or intellectual property-enabled markets. Though both are indeed important drivers of knowledge production, so are “knowledge commons,” which we should not take for granted.
Knowledge commons refers to institutionalised community governance of the sharing and, in many cases, creation and curation of intellectual and cultural resources. Examples range from scientific research commons, including data, literature, and research materials, to intellectual property pools, entrepreneurial/user innovation commons, rare-disease clinical research consortia, open-source software projects, and Wikipedia. Understanding how such communities share and develop knowledge is crucial in today's “information society.” ... [W]e have worked to systematise the study of knowledge commons and build a new field of interdisciplinary research in which law, economics, sociology, political science, network science, and other fields converge. Dozens of case studies have begun to reveal an empirical picture of knowledge commons.
Angela R McLean and Christopher Dye point out that the tragedy of the commons applied in the context of overuse of antibiotics and the resulting antimicrobial resistance:
It has become commonplace to refer to the rise of antimicrobial resistance (AMR) as a tragedy of the commons. Each individual wishes to use the common-pool resource of functioning antimicrobials whenever they might have a beneficial effect (whether in treating human illness or in raising livestock), but overuse accelerates the spread of drug-resistant pathogens, so the drugs become useless to all—and therein lies the tragedy. ...Whereas Hardin emphasized private or state ownership to achieve this, Ostrom argued that those who share in exploiting a common-pool resource can develop their own rules to prevent its overuse. She identified factors that are conducive to the establishment of effective institutions to regulate the exploitation of a resource: Users have common interests; they place a high value on the resource far into the future; users support effective monitoring; accurate information is valued and easily communicated; and it is feasible to establish binding and enforceable regulations. ...
Many of Ostrom's observations are starting to be fulfilled in the search for solutions to the problems of AMR, even if few people in this area explicitly set out to apply her work. The growing threat of AMR is increasingly understood by medical professionals, policy professionals, and the public alike. The associated discourse reflects the common, long-term interests of these diverse users. The widely accepted need for better surveillance of AMR signals rising support for effective monitoring and accurate, shared information. In a growing search for effective rules, physicians are adhering more strictly to evidence-based guidance for diagnosing infections; for infection control in hospitals; for procuring, prescribing and dispensing antimicrobials; and for ensuring that patients complete treatments. Beyond codes of practice, governments have in some settings introduced methods of enforcement, such as restricting the use of essential drugs to certified treatment centres. And public health specialists have called for AMR to be included among the International Health Regulations, a legally binding agreement to prevent the international spread of disease. Last, the global nature of the challenge is acknowledged in the World Health Organisation’s leadership in developing new norms for using existing antimicrobials and investing in new ones.
For economists, the tragedy of the commons is a memorable example of a situation where people pursuing their own self-interest will unleash a dynamic that leads to outcomes making everyone worse off than before. But the development of the idea has also brought forward the idea that while market coordination can fail, so can coordination through government and coordination through social customs. In some ways, the tragedy that ultimately underlies the "tragedy of the commons" is the recognition that gains from cooperation are possible, but not being achieved.
A version of this article first appeared on Conversable Economist.
Timothy Taylor is an American economist. He is managing editor of the Journal of Economic Perspectives, a quarterly academic journal produced at Macalester College and published by the American Economic Association. Taylor received his Bachelor of Arts degree from Haverford College and a master's degree in economics from Stanford University. At Stanford, he was winner of the award for excellent teaching in a large class (more than 30 students) given by the Associated Students of Stanford University. At Minnesota, he was named a Distinguished Lecturer by the Department of Economics and voted Teacher of the Year by the master's degree students at the Hubert H. Humphrey Institute of Public Affairs. Taylor has been a guest speaker for groups of teachers of high school economics, visiting diplomats from eastern Europe, talk-radio shows, and community groups. From 1989 to 1997, Professor Taylor wrote an economics opinion column for the San Jose Mercury-News. He has published multiple lectures on economics through The Teaching Company. With Rudolph Penner and Isabel Sawhill, he is co-author of Updating America's Social Contract (2000), whose first chapter provided an early radical centrist perspective, "An Agenda for the Radical Middle". Taylor is also the author of The Instant Economist: Everything You Need to Know About How the Economy Works, published by the Penguin Group in 2012. The fourth edition of Taylor's Principles of Economics textbook was published by Textbook Media in 2017.