A Gift that Keeps on Giving: The Contributions of Martin Weitzman to Environmental Economics

The world lost a remarkable scholar, a great economist, and a gentle soul on August 27th, when Martin Weitzman sadly passed away.

A week later, I was asked by the editors of the VOX CEPR Policy Portal (of the Centre for Economic Policy Research) – “research-based policy analysis and commentary from leading economists” ­– to write a brief intellectual biography and personal remembrance of Marty Weitzman, my colleague, friend, and long-time co-host of the Harvard Seminar on Environmental Economics and Policy.  In the essay I wrote, I sought to describe how Marty’s contributions have advanced the thinking of environmental and other economists, as well as the thoughts and actions of policymakers on many fundamental issues, including policy instrument choice, discounting, species diversity, and environmental catastrophes.  Today, I’m offering readers of this blog a slightly edited version of my Vox essay.

Photo Credit: Gernot Wagner

Martin Weitzman was a treasure – a gift that kept on giving to the research and policy worlds – for Harvard, for economists around the world, and for the global intellectual community. His work as an economic theorist who addressed a broad set of problems, and as an environmental economist who during the past decade focused on climate change, was unparalleled, and formed the basis for theoretical and empirical work carried out by legions of economists and other scholars around the world. His contributions to environmental economics in particular were unprecedented, and helped to shape the field for nearly five decades.

If economic theory is about stripping a problem down to its absolute essentials, and deriving meaningful insights from those essentials, then Weitzman was a master. Over and over again, Marty Weitzman demonstrated how careful and rigorous analysis of artfully constructed theoretical models can provide valuable and often surprising insights into difficult economic problems with real implications for the design of public policies.

Marty’s contributions have advanced the thinking of environmental economists and policymakers on policy instrument choice, discounting, species diversity, environmental catastrophes, and other fundamental issues. Across the board, the example of his rigorous and often ingenious work set high standards for theorizing in environmental economics and thereby served to elevate the entire field.

Brief intellectual biography

Born in New York City in 1942, Marty received his BA degree in mathematics and physics from Swarthmore College in 1963, and one year later, received an MS degree in statistics and operations research from Stanford University. In 1967, just three years after his Stanford degree, he was awarded a PhD degree in economics from the Massachusetts Institute of Technology (MIT), where his dissertation committee chair was Bob Solow. From 1967 to 1972, he taught in the Department of Economics at Yale University, then moved to MIT, where he taught in the Department of Economics until 1989, when he moved to Harvard University. He was a Professor of Economics at Harvard until 2018, when he became a Research Professor of Economics.

Economic planning

At the start of his research career, Weitzman studied centrally planned economies in a field that has all but disappeared from academic economics – comparative economic systems. It was during this early period of his career that Marty’s papers with titles such as ‘Soviet Postwar Economic Growth and Capital Labor Substitution’ (1970b) and ‘Iterative Multi-Level Planning with Production Targets’ (1970a) appeared.

A remarkable product of his interest in how to manage a centrally planned economy efficiently was Marty’s classic paper on ‘Prices vs. Quantities’ (1974). He began this work to address the question of whether prices or production quotas would lead to more efficient outcomes in a centrally planned economy (under conditions of uncertainty), but the paper and the subsequent literature evolved to address the question of whether a price instrument or a quantity instrument will be more efficient for environmental regulation.

Although Marty began his first forays into research and writing on environmental and natural resource problems in the 1970s (some of it developing Marxian views of common property problems), it was not until the 1990s that he turned with such passion and energy to this realm, and produced one important work after another that virtually span the field. That outpouring coincided with the beginning of my collaboration with Marty, co-hosting the Harvard Seminar on Environmental Economics and Policy (more on this below).

The share economy

Along the way, Weitzman carried out important research in macroeconomics and unemployment theory. One product of this – along with dozens of journal articles (inevitably in the top periodicals) – was his best-selling 1984 book, The Share Economy – which was eventually translated into seven languages. In this brief (167-page) book, Marty laid out his proposal for how the US economy could be protected from the dual threats of unemployment and inflation with a remarkably simple idea (a hallmark of many of his contributions) – namely that instead of companies paying workers in manufacturing a fixed wage, they be paid through something akin to profit sharing, in particular by paying workers a significant share of company revenue.

In short, this would provide incentives for companies to continue adding workers as long as, through their work, they added to company revenues. This ‘novel, seemingly workable plan for equipping the economy to resist the instabilities’ that had plagued it for more than a decade (Passell 1984), was labelled in the headline of a lead New York Times 1985 editorial, ‘the best idea since Keynes’.

Policy instrument choice: prices versus quantities

For environmental economists, Marty’s most prominent contribution is probably his classic 1974 article, ‘Prices vs. Quantities’, which developed the simultaneously simple and powerful insight that – under conditions of uncertainty – the expected relative efficiency of policy instruments based on prices (such as a pollution tax) versus those based on quantities (such as a cap-and-trade system) depends on the relative slopes of the expected marginal benefit and marginal cost functions.

That work remains one of the most frequently cited articles in all of environmental economics. It stimulated a massive literature, a fact that prompted Richard Newell (Resources for the Future) to characterize the work as a ‘gift that keeps on giving’ at a symposium we held at Harvard in October 2018 to mark Marty’s retirement and celebrate his contributions, ‘Frontiers in Environmental Economics and Policy: A Symposium in Honor of Martin L Weitzman’. Even now, Marty’s 1974 paper is at the core of analysis of carbon taxes versus carbon cap-and-trade systems to address climate change (Karp and Traeger 2018; Mideksa and Weitzman 2019; Stavins 2019).

Colleagues who spoke at the celebration of Marty’s work on October 11, 2018, at the Harvard Kennedy School, “Frontiers in Environmental Economics and Policy: A Symposium in Honor of Martin L. Weitzman.” Front Row, left to right: Michael Greenstone, University of Chicago; Maureen Cropper, University of Maryland; Martin L. Weitzman, Harvard University; Robert Pindyck, Massachusetts Institute of Technology; William Nordhaus, Yale University. Back Row, left to right: James Stock, Harvard University; Charles Kolstad, Stanford University; Lawrence Goulder, Stanford University; Robert Stavins, Harvard University; Richard Newell, Resources for the Future. Photo Credit: Martha Stewart

Biodiversity

In the early 1990s, Weitzman responded to what he sensed might be the unwillingness – or the inability – of ecologists to rank ecologies in terms of their relative biodiversity, by producing a series of brilliant treatments of how these comparisons can be made quantitatively and rigorously: ‘On Diversity’ (1992); ‘What to Preserve: An Application of Diversity Theory to Crane Conservation’ (1993); ‘Patterns of Behavior in Biodiversity Preservation’ (Metrick and Weitzman 1996); and ‘The Noah’s Ark Problem’ (1998a). At the Harvard symposium, Charlie Kolstad (Stanford University) cited this body of work for its ‘significance and importance’.

Discounting

It was also in the 1990s that Marty became interested in a central issue of the economic analysis of climate change policies, namely long-term discounting. Given the long time horizons of the climate change problem, analysis of the expected net present value of alternative policies can be dominated by the choice of discount rate, which – with conventional exponential discounting – will greatly diminish the relative quantitative importance of phenomena that are decades or longer in the future.

Through careful theoretical analysis, Marty concluded that rather than a constant discount rate being employed, a rate that itself is diminishing over time is appropriate, so that benefits and costs in the near future would be subject to a typical rate, while benefits and costs further in the future would be subject to a much lower rate.

This important and influential work appeared in a series of articles, including: ‘On the Environmental Discount Rate’ (1994); ‘Why the Far-Distant Future Should be Discounted at its Lowest Possible Rate’ (1998b); and ‘Gamma Discounting’ (2001a). At the Harvard symposium, Larry Goulder (Stanford University) emphasized that this work is important ‘because it affects decisions as to how much we should invest in infrastructure, in mitigation, and in other realms.’

Green national accounting

A topic that has pervaded decades of analysis and commentary in the environmental sphere is the reality that conventional measures of economic growth, such as gross domestic product, are not measures of welfare, since they do not account for externalities (among other non-market economic phenomena). In 1999, the National Research Council published Nature’s Numbers: Expanding the National Economic Accounts to Include the Environment, produced by a committee chaired by Bill Nordhaus and including Marty Weitzman (Nordhaus and Kokkelenberg 1999). That was linked with several contributions that Weitzman subsequently made to the scholarly literature, including: ‘Does NNP Growth Indicate Welfare Improvement’ (Asheim and Weitzman 2001); and ‘A Contribution to the Theory of Welfare Accounting’ (2001b).

At the Harvard symposium, Bill Nordhaus emphasized Marty’s contributions in this realm, and launched his keynote presentation, ‘The Intellectual Footprint of Martin Weitzman in Environmental Economics’, by stating that Marty ‘has changed the way we think about economics and the environment.’ He concluded that ‘those who claim that environmental regulations hurt growth are completely wrong, because they are using the wrong yardstick. Pollution should be in our measures of national output, but with a negative sign, and if we use green national output as our standard, then environmental and safety regulations have increased true economic growth substantially in recent years… For this important insight we applaud Martin Weitzman, a radically innovative spirit in economics.’

Fisheries

Some will be surprised to learn that a theorist such as Marty Weitzman was as immersed as he was in concerns about the real world of natural resource management and environmental protection. One example comes from his research and outreach in the realm of fisheries management. His modelling of Icelandic commercial fisheries affected thinking and discussion around the world regarding the use of taxes and quotas to regulate open-access fisheries.

As Maureen Cropper (University of Maryland) said at the Harvard symposium, ‘this is another example of the use of a simple model and treatment of uncertainty that really did start a conversation among fisheries economists’. This application of Weitzman’s previously developed theory of instrument choice was documented in his 2002 paper ‘Landing Fees vs Harvest Quotas with Uncertain Fish Stocks’.

Fat tails

In recent years, Marty made prominent and important contributions to thinking about long-term climate change policy with his development of a theory of how positive biophysical feedback loops could lead to uncertainty about the damages of climate change that is best characterized by a probability distribution of damages with fat tails, such as a Pareto distribution, rather than a conventional Gaussian (normal) distribution. The result is greater weight being given to catastrophic (but relatively small probability) outcomes.

Speaking at the Harvard symposium, Bob Pindyck of MIT pointed to Weitzman’s prescient 2007 paper, ‘Subjective Expectations and Asset-Return Puzzles’ as having had a profound influence on Marty’s subsequent modelling of catastrophic climate change. A small subset of the papers Marty published on this topic include: ‘On Modeling and Interpreting the Economics of Catastrophic Climate Change’ (2009); ‘Fat-Tailed Uncertainty in the Economics of Climate Change’ (2011); and ‘Fat Tails and the Social Cost of Carbon’ (2014b).

Domestic and international climate change policy

Marty Weitzman always searched for topics for his research that were not only interesting, but also relevant and important for real-world applications. His recent work exploring alternative policy instruments to address climate change and his critical examinations of the form of international climate agreements provide telling examples of this. It was in this regard that Jim Stock (Harvard University) credited Weitzman for the ‘tremendous influence’ his ideas have had on the formulation of public policy around the world.

Just a few of the many papers that could be cited in this context are: ‘Can Negotiating a Uniform Carbon Price help to Internalize the Global Warming Externality’ (2014a); ‘A Voting Architecture for the Governance of Free-Driver Externalities, with Application to Geoengineering’ (2015); and ‘On a World Climate Assembly and the Social Cost of Carbon’ (2017). Also, of course, Marty and his former student, Gernot Wagner, wrote a lucid and compelling book, Climate Shock: The Economic Consequences of a Hotter Planet (2015).

Theoretical foundations for empirical analyses

It should be emphasized that Marty Weitzman’s theoretical work was not only important for other theorists, but also for empirical economists. In many of the realms described above, his insights were fundamental as the foundation for sound empirical analysis. As Michael Greenstone (University of Chicago) noted at the Harvard symposium, Marty’s work ‘takes something you are kind of confused about, and then after you read it, you can’t understand how in the world you were confused beforehand. It just clarifies things in a way that is really beautiful.’

A remarkable scholar

Marty Weitzman was thus a real treasure – a ‘gift that kept on giving’ – for both the research and policy worlds. His work as a theorist on environment broadly and on climate change in particular was unparalleled, and formed the basis of much theoretical and empirical research carried out by others over several decades. His work – from examining price versus quantity instruments in the early 1970s through his examinations in the last few years of the implications of fat tails in the probability distribution of possible climate damages – have changed the way economists and others think about the environment and policies to protect it.

His contributions were well recognized. He was elected a Fellow of the Econometric Society in 1976; a Fellow of the American Academy of Arts and Sciences in 1986; three times won the annual award for ‘Publication of Enduring Quality’ from the Association of Environmental and Resource Economists; received the 20th Anniversary Prize from Fondazione Eni Enrico Mattei, the Leontief Prize, and the Eric Kempe Prize in 2011; and the John Kenneth Galbraith Award in 2013.

Memories

My greatest personal remembrance will be that I learned an immense amount from Marty by co-hosting with him for 26 years the Harvard Seminar on Environmental Economics and Policy. That’s 52 semesters involving more than 400 seminars, each with a distinct paper and presentation by a leading scholar from across the United States and around the world. I found that Marty’s questions and comments were often as insightful as the speaker’s presentation.

Of course, we did not always agree. I remember our spirited discussions contrasting Marty’s strong view of the superiority of carbon taxes and my view of the relative symmetry of price and quantity instruments for climate change. Also we had some long discussions about the 2015 Paris Agreement on climate change, which Marty saw (accurately) for what it lacks, and I saw for its improvements over the international policy architecture that had preceded it. We disagreed, but were never disagreeable (and I never succeeded in changing his mind!). All in all, for three decades, I consistently learned from this remarkable scholar. He truly was a gift that kept on giving.

Marty receiving from the author a book of testimonials by 100 scholars around the world at the celebration of Marty’s work on October 11, 2018, at the Harvard Kennedy School, “Frontiers in Environmental Economics and Policy: A Symposium in Honor of Martin L. Weitzman.” Photo Credit: Martha Stewart

REFERENCES

Asheim, Geir B, and Martin L Weitzman (2001), ‘Does NNP Growth Indicate Welfare Improvement?’ Economic Letters 73(2): 233-39.

Karp, Larry, and Christian Traeger (2018), ‘Prices versus Quantities Reassessed’, CESifo Working Paper No. 7331.

Metrick, Andrew, and Martin L Weitzman (1996), ‘Patterns of Behavior in Endangered Species Preservation’, Land Economics 72(1): 1-16.

Mideksa Torben, and Martin L Weitzman (2019), ‘Prices versus Quantities across Jurisdictions’, Journal of the Association of Environmental and Resource Economists 6(5): 883-891.

New York Times (1985), ‘Best Idea Since Keynes’, Editorial, March 28, Section A, page 30.

Nordhaus, William D, and Edward C Kokkelenberg, editors (1999), Nature’s Numbers: Expanding the National Economic Accounts to Include the Environment, Panel on Integrated Environmental and Economic Accounting, National Academy Press.

Nordhaus, William D (2019), ‘The Intellectual Footprint of Martin Weitzman in Environmental Economics’, presentation at ‘Frontiers in Environmental Economics and Policy: A Symposium in Honor of Martin L. Weitzman’, Harvard Kennedy School, October 11.

Passell, Peter (1984), ‘The Editorial Notebook: The Hidden Boon in Profit-Sharing’, New York Times, November 15, Section A, Page 30.

Stavins, Robert N (2019), ‘The Future of U.S. Carbon-Pricing Policy’, NBER Working Paper No. 25912 (http://www.nber.org/papers/w25912).

Wagner, Gernot, and Martin L Weitzman (2015), Climate Shock: The Economic Consequences of a Hotter Planet, Princeton University Press.

Weitzman, Martin L (1970a), ‘Iterative Multi-Level Planning with Production Targets’, Econometrica 38(1): 50-65.

Weitzman, Martin L (1970b), ‘Soviet Postwar Economic Growth and Capital Labor Substitution’, American Economic Review 60 (4): 676-92.

Weitzman, Martin L (1974), ‘Prices vs. Quantities’, Review of Economic Studies 41(4): 477-91.

Weitzman, Martin L (1984), The Share Economy, Harvard University Press.

Weitzman, Martin L (1992), ‘On Diversity’, Quarterly Journal of Economics 107(2): 363-405.

Weitzman, Martin L (1993), ‘What to Preserve: An Application of Diversity Theory to Crane Conservation’, Quarterly Journal of Economics 108(1): 157-83.

Weitzman, Martin L (1994), ‘On the ‘Environmental’ Discount Rate’, Journal of Environmental Economics and Management 26: 200-9.

Weitzman, Martin L (1998a), ‘The Noah’s Ark Problem’, Econometrica 66(6): 1279-98.

Weitzman, Martin L (1998b), ‘Why the Far-Distant Future Should be Discounted at its Lowest Possible Rate’, Journal of Environmental Economics and Management 36(3): 201-8.

Weitzman, Martin L (2001a), ‘Gamma Discounting’, American Economic Review 91(1): 260-71.

Weitzman, Martin L (2001b), ‘A Contribution to the Theory of Welfare Accounting’, Scandinavian Journal of Economics 103(1): 1-23.

Weitzman, Martin L (2002), ‘Landing Fees vs Harvest Quotas with Uncertain Fish Stocks’, Journal of Environmental Economics and Management 43: 325-38.

Weitzman, Martin L (2007), ‘Subjective Expectations and Asset-Return Puzzles’, American Economic Review 97(4): 1102-30.

Weitzman, Martin L (2009), ‘On Modeling and Interpreting the Economics of Catastrophic Climate Change’, Review of Economics and Statistics 91(1): 1-19.

Weitzman, Martin L (2011), ‘Fat-Tailed Uncertainty in the Economics of Catastrophic Climate Change’, Review of Environmental Economics and Policy 5(2): 275-92.

Weitzman, Martin L (2014a), ‘Can Negotiating a Uniform Carbon Price Help to Internalize the Global Warming Externality?’, Journal of the Association of Environmental and Resource Economists 1(1/2): 29-49.

Weitzman, Martin L (2014b), ‘Fat Tails and the Social Cost of Carbon’, American Economic Review Papers and Proceedings 104(5): 544-6.

Weitzman, Martin L (2015), ‘A Voting Architecture for the Governance of Free-Driver Externalities, with Application to Geoengineering’, Scandinavian Journal of Economics 117(4): 1049-68.

Weitzman, Martin L (2017), ‘On a World Climate Assembly and the Social Cost of Carbon’, Economica 84(336): 559-86.

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Economics of the Environment

The seventh edition of Economics of the Environment: Selected Readings has just been published by Edward Elgar Publishing, and I’m pleased to bring this new volume to your attention.  The book is a compendium of some of the best and most timely articles by a dream team of environmental economists.  Previous editions have served as a valuable supplement to environmental economics text books or as a stand-alone reference book of key, up-to-date readings from the field.  In addition to being valuable for anyone studying environmental economics, environmental policy, or climate change policy, the book can be a useful resource for practitioners in government, private industry, as well as advocacy groups and other NGOs working on environmental policy.

In today’s essay, I first describe the background and motivation for the book, summarize its contents – chapter by chapter, highlight its key messages, and then conclude with some reflections and an invitation.

Background and Motivation

Environmental and natural resource problems are both more widespread and more important today than they were 100 years ago when the discipline of modern economics was marking its emergence with the publication of the first volume of the American Economic Review. A century of economic growth and globalization have brought unparalleled improvements in societal well-being, but also unprecedented challenges to the carrying capacity of the planet. Increases in income and population that would have been inconceivable 100 years ago have greatly heightened pressures on the natural environment.

The stocks of a variety of renewable natural resources – including water, forests, fisheries, and numerous other species of plant and animal – have been depleted below socially-efficient levels, principally because of market failures. Open-access – whether characterized as externalities or public goods – have led to the degradation of air and water quality, inappropriate disposal of hazardous waste, depletion of stratospheric ozone, and the atmospheric accumulation of greenhouse gases linked with global climate change.

Over the same century, economics as a discipline has gradually come to focus more and more attention on these problems, first considering natural resources and subsequently environmental quality. Economic research within academia and think tanks has improved our understanding of the causes and consequences of excessive resource depletion and inefficient environmental degradation, and thereby has helped identify sensible policy solutions.

Despite the generally positive influence economics has had on policy, the problems have overall not diminished, and the lag between understanding and action can be long. While some environmental problems have been addressed successfully, others continue to emerge. Some, such as the threat of global climate change, are both more consequential and more difficult than problems of the past. Fortunately, economics is well positioned to offer better understanding and better policies to address these new and ongoing challenges.

The Book

Approximately six years have passed since the previous edition of this volume was published, and it is now close to 50 years since the first edition appeared in 1972, edited by Robert and Nancy Dorfman. I have had the pleasure of editing the fourth (2000), fifth (2005), sixth (2012), and now the seventh edition (2019) of this book. Whereas the first six editions were published by W.W. Norton & Company, the new edition has been published by Edward Elgar Publishing Limited.

Over this span of time, environmental economics has evolved from what was once a relatively obscure application of welfare economics to a prominent field of economics in its own right. The number of articles on the natural environment appearing in mainstream economics periodicals has continued to increase, as has the number of economics journals dedicated exclusively to environmental and resource topics.

There has also been a proliferation of environmental economics textbooks. Many are excellent, but none can be expected to provide direct access to timely and original contributions by the field’s leading scholars. As most teachers of economics recognize, it is valuable to supplement the structure and rigor of a text with original readings from the literature.

With that in mind, this new volume consists of 34 chapters that instructors will find to be of tremendous value as a complement to their chosen text and their lectures. The scope is comprehensive, the list of authors is a veritable “who’s who” of environmental economics, and the articles are timely, with more than 94 percent published since 1990, and well more than a third published over the past five years. Overall, more than half of the chapters are new to this edition.

In order to make these readings broadly accessible, one criterion I used in the selection process is that articles should not only be original and well written – and meet the highest standards of economic scholarship – but also be non-technical in their presentations. Hence, readers will find little or no formal mathematics in the book’s 688 pages.

The 34 chapters are grouped into nine parts of the book:  (1) Overview; (2) Costs and Benefits of Environmental Protection; (3) Assessing the Goals of Environmental Policy:  Economic Efficiency and Benefit-Cost Analysis; (4) The Means of Environmental Policy:  Cost-Effectiveness and Market-Based Instruments; (5) Economics of Natural Resources; (6) Global Climate Change; (7) Sustainability, the Commons, and Globalization; (8) Behavioral Economics and the Environment; and (9) Economics and Environmental Policy Making.

Overview

Part I of the volume provides an overview of the field and a review of its foundations. Don Fullerton and I (Chapter 1) start things off with a brief essay about how economists think about the environment. This is followed by the classic treatment of social costs and bargaining by Ronald Coase (Chapter 2).

Costs and Benefits of Environmental Protection

Part II examines the costs and benefits of environmental protection. It begins with an article by Antoine Dechezleprêtre and Misato Sato (Chapter 3) that examines an often-controversial area, namely the theory and empirical evidence regarding the relationship between environmental regulation and so-called “competitiveness.” The remainder of Part II focuses on the other, more challenging side of the analytic ledger – the benefits of environmental protection. This is an area that has been even more contentious, both in the policy world and among scholars. Here the core question is whether and how environmental amenities can be valued in economic terms for analytical purposes. Trudy Cameron (Chapter 4) provides a valuable guide to a concept that is both important in assessments of the benefits of environmental regulations and is also widely misunderstood – the value of a statistical life. Then we turn to a provocative debate on the stated-preference method known as “contingent valuation,” including two supportive essays – by Richard Carson (Chapter 5) and by Catherine Kling, Daniel Phaneuf, and Jinhua Zhao (Chapter 6) – followed by a critique by Jerry Hausman (Chapter 7).

Assessing the Goals of Environmental Policy:  Economic Efficiency and Benefit-Cost Analysis

There are two principal policy questions that need to be addressed in the environmental realm: how much environmental protection is desirable; and how should that degree of environmental protection be achieved?

In Part III, the criterion of economic efficiency and the analytical tool of benefit–cost (net present value) analysis are considered as ways of assessing the goals of environmental policies. In an introductory essay, Kenneth Arrow and his co-authors (Chapter 8) ask whether there is a role for such analysis to play in environmental, health, and safety regulation. Then, Lawrence Goulder and I (Chapter 9) focus on a key ingredient of benefit–cost analysis that non-economists often find confusing or even troubling – intertemporal discounting. Next, Kenneth Arrow and another set of co-authors (Chapter 10) focus on the possibility of a declining discount rate, which can be very important for analyzing long-term phenomenon, such as climate change. Finally, Ted Gayer and Kip Viscusi (Chapter 11) provide a critique of what they perceive to be the ways in which the principles of benefit–cost analysis have been abused in some regulatory impacts analyses carried out by the federal government.

The Means of Environmental Policy:  Cost Effectiveness and Market-Based Instruments

Part IV examines the policy instruments – the means – that can be employed to achieve environmental targets or goals. This is an area where economists have made their greatest inroads of influence in the policy world, with tremendous changes over the past 30 years in the reception given by politicians and policy makers to so-called market-based or economic-incentive instruments for environmental protection. Richard Schmalensee and I (Chapter 12) start things off by identifying lessons that have been learned from three decades of experience with cap-and-trade systems in Europe and the United States. In the next chapter, Schmalensee and I (Chapter 13) examine the ironic history of one particularly important application – the SO2 allowance trading system, enacted by the Clean Air Act Amendments of 1990. The following article, by Karen Fisher-Vanden and Sheila Olmstead (Chapter 14), recognizes that virtually all prominent applications of emissions trading systems have been for air pollutants of various types, and examines the opportunities and challenges of using such instruments to address water quality problems.

Economics of Natural Resources

Part V consists of four essays on the economics of natural resources, beginning with Robert Solow’s classic, intuitive explication of Harold Hotelling’s seminal contribution to the economic theory of nonrenewable natural resources (Chapter 15). A natural extension is provided by Thomas Covert, Michael Greenstone, and Christopher Knittel (Chapter 16) in an article in which they ask whether market forces of supply and demand will lead to severe reductions in the use of fossil fuels. Then Sheila Olmstead (Chapter 17) applies similar thinking to the management of water resources, and Severin Borenstein (Chapter 18) examines the economics of renewable electricity generation.

Global Climate Change

The next four sections of the book treat a set of timely and important topics and problems. Part VI is dedicated to analysis of economic dimensions of global climate change, which appears to be the most significant environmental problem that has yet arisen, both in terms of its potential damages and in terms of the costs of addressing it. First, a broad overview of the topic is provided in a survey article by Joseph Aldy, Alan Krupnick, Richard Newell, Ian Parry, and William Pizer (Chapter 19). Next, William Nordhaus (Chapter 20) critiques the well-known Stern Review on the Economics of Climate Change, and Nicholas Stern and Chris Taylor (Chapter 21) respond. Following this, Richard Newell, William Pizer, and Daniel Raimi (Chapter 22) examine what was accomplished with the use of carbon markets in various parts of the world in the 15 years after the global climate agreement known as the Kyoto Protocol. Of course, after Kyoto, the next major global agreement in this realm was the landmark Paris Agreement of 2015. Daniel Bodansky, Seth Hoedl, Gilbert Metcalf, and I (Chapter 23) analyze how linking heterogeneous national policies can lower the cost of achieving national targets and thereby facilitate increased ambition under the Paris Agreement. Finally, Richard Tol (Chapter 24) turns from the cost side to the benefit side of climate policy by examining the anticipated economic impacts of unabated climate change.

Sustainability, the Commons, and Globalization

Part VII examines another important area of exploration in environmental economics: sustainability, the commons, and globalization. Robert Solow (Chapter 25) begins with an economic perspective on sustainability. This is followed by Elinor Ostrom’s development of a general framework for analyzing sustainability (Chapter 26), and my own historical view of economic analysis of problems associated with open-access resources (Chapter 27). Then, we turn to the topic of corporate social responsibility and the environment, discussion of which has too often been characterized by more heat than light. Forest Reinhardt, Richard Vietor, and I (Chapter 28) provide an economic perspective by examining the notion of firms voluntarily sacrificing profits in the social interest. The essays in the book can apply in the context of a diverse set of countries, but developing countries face a special set of challenges. So, this section closes with Michael Greenstone and Kelsey Jack (Chapter 29) providing a broad examination of the relationship between economic development and environmental protection.

Behavioral Economics and the Environment

Next, in Part VIII, we feature applications of the emerging area of behavioral economics to environmental issues, beginning with an overview of this terrain by Jason Shogren and Laura Taylor (Chapter 30). Then, Cass Sunstein and Lucia Reisch (Chapter 31) examine the implications of behavioral economics for the types of public policies that are most likely to be effective. Lastly, a specific application of behavioral economics to environmental questions is considered by Todd Gerarden, Richard Newell, and myself (Chapter 32), as we examine potential explanations for the so-called “energy paradox” or “energy efficiency gap” – the apparent reality that energy-efficiency technologies that would more than justify their upfront costs through life-cycle energy-cost savings are nevertheless not adopted.

Economics and Environmental Policy Making

The final section of the book, Part IX, departs from the normative concerns of much of the volume to examine some interesting and important questions of political economy. It turns out that an economic perspective can provide useful insights into questions that might at first seem fundamentally political. Myrick Freeman (Chapter 33) reflects on the benefits that U.S. environmental policies have brought about since the first Earth Day in 1970. And Robert Hahn (Chapter 34) addresses the question that many of the articles in this volume raise: what impact has economics actually had on environmental policy?

Key Messages

Preparing the various editions of this book has caused me to review hundreds of articles, and this has allowed me to identify some common themes that have emerged. First, there is the value – or at least, the potential value – of economic analysis of environmental policy. The cause of virtually all environmental problems in a market economy is economic behavior (that is, imperfect markets affected by externalities), and so economics offers a powerful lens through which to view environmental problems, and therefore a potentially effective set of analytical tools for designing and evaluating environmental policies.

A second message, connected with the first, is the specific value of benefit–cost analysis for helping to promote efficient policies. Economic efficiency ought to be one of the key criteria for evaluating proposed and existing environmental policies. Despite its limitations, benefit–cost analysis can be useful for consistently assimilating the disparate information that is pertinent to sound decision making. If properly done, it can be of considerable help to public officials when they seek to establish or assess environmental policies.

Third, the means governments use to achieve environmental objectives matter greatly. Different policy instruments have very different implications in terms of both benefits and costs, including abatement costs in both the short and the long term. Market-based instruments can enable the minimization of these costs.

Fourth, an economic perspective is also of value when reflecting on the use of natural resources, whether land, water, fisheries, or forests. Excessive rates of depletion are frequently due to the nature of the respective property-rights regimes, in particular, common property and open-access. Economic instruments – such as ITQ systems in the case of fisheries – can and have been employed to bring harvesting rates down to socially efficient levels.

Fifth and finally, policies for addressing global climate change, linked with emissions of carbon dioxide and other greenhouse gases, can benefit greatly from the application of economic thinking. On the one hand, the long time-horizon of climate change, the profound uncertainty in quantitative links between emissions and actual damages, and the possibility of catastrophic climate change present significant challenges to conventional economic analysis. But, at the same time, the ubiquity of energy generation and use in modern economies means that only market-based policies – essentially carbon-pricing regimes – are feasible instruments for achieving truly meaningful emissions reductions. Hence, despite the challenges, an economic perspective on this grandest of environmental threats is essential.

Reflections and an Invitation

Environmental economics is a rapidly evolving field. Not only do new theoretical models and improved empirical methods appear on a regular basis, but entirely new areas of investigation open up when the natural sciences indicate new concerns or the policy world turns to new issues. Therefore, this volume of collected essays remains a work in progress. I owe a great debt of gratitude to the teachers, students, and other readers of previous editions who have sent their comments and suggestions for revisions. Thanks are also due to Patrick Behrer, who provided superb research assistance in producing this Seventh Edition. Looking to future editions, I invite all readers – whether teachers, students, or practitioners – to send me your suggestions for improvement.

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Martin Weitzman’s Contributions to Environmental Economics

Many of the world’s most eminent economists and climate scientists gathered on October 11th, 2018, at Harvard Kennedy School to celebrate and honor the career of Martin L. Weitzman, professor of economics at Harvard University, who is “retiring” following four decades of research and writing which have illuminated thought and policy across a broad range of important realms. During his “retirement,” Marty will serve as a Research Professor in Harvard’s Department of Economics.

The October 11th event, “Frontiers in Environmental Economics and Policy: A Symposium in Honor of Martin L. Weitzman,” which drew about 250 people, was organized and hosted by the Harvard Environmental Economics Program (HEEP), with additional support from the Harvard University Center for the Environment and the Mossavar-Rahmani Center for Business and Government at the Kennedy School.

A video of the entire event is available here.

Having learned so much from Marty Weitzman, including during the 26 years that he and I have been co-hosting the Harvard Seminar in Environmental Economics and Policy, I was delighted to moderate the symposium.  From the earliest days of planning the event until the day of the symposium, my team – Rob Stowe, HEEP Executive Director, Jason Chapman, HEEP Program Manager, and Casey Billings, HEEP Program Coordinator – and I were inspired by the breathtaking contributions Marty has made to the once-emerging and now mature global discipline of environmental economics.

In my blog essay today, I want to provide for those who could not attend a sense of what it was like to be there, and remind those who did attend what transpired.

Introducing Professor William Nordhaus

I began the symposium by introducing our keynote speaker, William D. Nordhaus, who just a few days earlier had been announced as a recipient of this year’s Nobel Prize in Economics for his work on modeling the economics of climate change and related public policies.

The cliche that “our speaker needs no introduction” certainly applied here, and so I was very brief, noting first that for nearly four decades, Bill Nordhaus has written about the economics of the environment.  Building on his background as a macro-economist concerned about economic growth, Bill began to give particular attention to the role of energy generation and use in the 1970s, not long after beginning his academic career.  What is truly remarkable is that it was in the early 1980s that he began working on the economics of global climate change, long before most other economists were even aware of the problem, let alone analyzed it.

Bill has been on the faculty at Yale University since 1967, where he is the Sterling Professor of Economics, and Professor in Yale’s School of Forestry and Environmental Studies.  He is a member of the National Academy of Sciences, a Fellow of the American Academy of Arts and Sciences, a Distinguished Fellow of the American Economic Association, and a Research Associate of the National Bureau of Economic Research.  In addition to his many scholarly achievements, he served as a Member of the President’s Council of Economic Advisers in the Carter administration.

What is particularly striking about Bill Nordhaus’s contributions is that — as long as I can remember — he has made his path-breaking DICE model of global climate change economics accessible to and usable by other researchers around the world.

Keynote Address by Bill Nordhaus

Bill launched his presentation, “The Intellectual Footprint of Martin Weitzman in Environmental Economics,” by stating that Marty “has changed the way we think about economics and the environment.”  He then went on to itemize Weitzman’s impressive body of work, including his series of studies on the share economy; his research on the Soviet Union and central planning; his seminal 1974 paper, “Prices vs. Quantities,” which provided fresh insight on how regulatory policy can best be leveraged to maximize public good; and his work on so-called “fat tails” and the “dismal theorem,” which questioned the value of a standard benefit-cost analysis when conditions could result in catastrophic events, even if the probability of such events is very low.

But Nordhaus devoted much of his talk to highlighting Weitzman’s extraordinary contributions to the field of environmental economics, in particular, the economics of climate change and climate change policy. It was Weitzman’s “revolutionary” series of papers on the ideal measures of national income, Nordhaus stated, that focused early attention on the need to take the harmful impacts of pollution into account when tabulating the gross domestic product (GDP), a concept referred to as “Green GDP.”

“Our output measures do not include pollution,” said Nordhaus. “They include goods like cars and services like concerts and education, but they do not include CO2 that is pumped into the atmosphere.”  He explained that pollution abatement measures are often blamed for causing a drag on the economy, but aren’t credited for the health and welfare benefits they create.

“If our incomes stay the same but we are healthier, and live a year longer or ten years longer, that will not show up in the way we measure things,” Nordhaus remarked. “But we can apply these Weitzman techniques to value improvements in health and happiness.”

“Those who claim that environmental regulations hurt growth are completely wrong, because they are using the wrong yardstick,” Bill continued. “Pollution should be in our measures of national output, but with a negative sign, and if we use green national output as our standard, then environmental and safety regulations have increased true economic growth substantially in recent years…For this important insight we applaud Martin Weitzman, a radically innovative spirit in economics.”

A Panel of Leading Environmental Economists

Following the keynote address by Nordhaus, I welcomed to the stage fellow economists Maureen Cropper, Lawrence Goulder, Michael Greenstone, Charles Kolstad, Richard Newell, Robert Pindyck, and James Stock for a lively panel discussion.  Each of these economists have themselves made important contributions to scholarship and policy in the environmental realm.

To each panelist, I posed a question about a different aspect of Marty Weitzman’s key contributions – ranging from climate change policy to biodiversity and fisheries management.

First, Richard Newell, the President and CEO of Resources for the Future (RFF) and a former student of Weitzman when he studied for his Ph.D. in Public Policy at the Harvard Kennedy School, described Weitzman’s seminal paper, “Prices vs. Quantities”, as a “gift that keeps on giving” for economists and policy makers invested in improving regulatory policy.

Next, Charlie Kolstad, a Senior Fellow at the Stanford Institute for Economic Policy Research, focused on Marty Weitzman’s research on biodiversity, and cited it for its “significance and importance.”

Third up was Larry Goulder, the Shuzo Nishihara Professor of Environmental and Resource Economics at Stanford University and a former colleague of Weitzman in the Harvard Department of Economics.  Larry described the importance of Marty’s work on long-term discounting, and commended his 1998 paper on declining discount rate profiles, noting that it has affected public policies in Denmark, France, and Norway, as well as public discussion in the Netherlands, Sweden, and elsewhere. Larry noted that “it’s very important, because it affects decisions as to how much we should invest in infrastructure, in mitigation, and in other realms.”

Fourth on the panel was Bob Pindyck, the Bank of Tokyo-Mitsubishi Professor of Economics and Finance at the Sloan School of Management at MIT, who is very familiar with Marty Weitzman’s work on fat-tailed distributions, and has contributed to that literature himself.  Bob cited Weitzman’s prescient 2007 paper “Subjective Expectations and Asset-Return Puzzles” for its significant influence upon the later modeling of the economics of catastrophic climate change.

Next was Jim Stock, the Harold Hitchings Burbank Professor of Political Economy at Harvard University.  I asked Jim to comment on the effect of Marty’s work on the policy world.  Jim started by crediting Weitzman for the “tremendous influence” his ideas have had upon the formation of public policy in the United States and around the world, citing the nine-state Regional Greenhouse Gas Initiative (RGGI), and the Clean Power Plan introduced by President Obama in 2015.

Sixth on the panel was Maureen Cropper, Distinguished University Professor and Chair of the Department of Economics at the University of Maryland.  Maureen had kindly agreed to talk about Marty Weitzman’s research and outreach in the realm of fisheries management.  Maureen explained that his modeling work in Iceland and elsewhere had affected thinking and discussion around the world regarding the use of taxes and quotas to regulate fishing industries. “This is another example of the use of a simple model and treatment of uncertainly that really did start a conversation among fisheries economists when it came out,” she said.

Finally Michael Greenstone, the Milton Friedman Professor in Economics at the University of Chicago, agreed to reflect on how Weitzman’s theoretical insights were fundamental as the foundation for sound empirical analysis.  Greenstone noted that Marty’s work “takes something you are kind of confused about, and then after you read it, you can’t understand how in the world you were confused beforehand. It just clarifies things in a way that is really beautiful.”

A Book of Testimonials

Many of those who attended the symposium — and many who were not able to join us — wanted to tell Marty directly how they feel about him and his work.  And so we assembled and presented to Marty a book in which we had compiled 60 testimonial letters, including from some of his admirers who could not be with us at the symposium, such as:  Orley Ashenfelter, Greg Mankiw, Kerry Smith, Bob Solow, Nick Stern, Cass Sunstein, and others.  As I presented Marty with the book of letters, I took a moment to read aloud from just one of the letters from another person who could not be with us:

When I was an undergraduate in the economics department at MIT, you were a bright and rising young star.  Later, as a faculty member, I routinely assigned your papers to my environmental economics students.  Your scholarship and your leadership enriched their experiences — and mine — tremendously.

I will never forget when you announced that you were moving on to Harvard — what a blow! —but the universe has seen fit to bring us together once again.  It is an honor to acknowledge your extraordinary contributions to the field, and to thank you for shining a light for all of us.

                                                      All the best,

                                                             Larry

                                                      Lawrence Bacow, President, Harvard University

More Memories

The book did not end with the testimonial letters.  On a personal note, it has been 26 years since Marty Weitzman and I launched the Harvard Seminar in Environmental Economics and Policy.  Over those 52 semesters, we have hosted a total of 398 seminars!  In the very first semester — the fall of 1992 — the seminar presenters included, among others, in alphabetical order: Bill Nordhaus, Kerry Smith, Bob Solow, Rob Stavins, Kip Viscusi, and Marty Weitzman.

In virtually every one of these 400 seminars, everyone in the seminar room – including me — learned not only from each seminar’s presenter, but from Marty’s concise and relevant questions which would inevitably go directly to the heart of the matter.  So, I was pleased to include in the book copies of all 52 seminar schedules, beginning with the fall of 1992 and culminating with the fall of 2018.  I will not say “concluding” with the fall of 2018, because I trust that my collaboration with Marty, which I have valued highly, will continue.

Marty Weitzman has been a treasure for Harvard and for the global scholarly community.  All of us are confident that his contributions will continue to be forthcoming.

Marty Weitzman Responds

Following the Symposium, Weitzman took several minutes to reflect on his remarkable career, recognizing that while he has pursued projects across multiple disciplines, his research would often hit dead ends.

“I’m drawn to things that are conceptually unclear, where it’s not clear how you want to make your way through this maze,” he said. “It’s difficult to describe a creative process, but I get some sort of an inspiration…Most of the time it’s a waste of time because I can’t formalize it, so I try and try and just nothing comes of it. But occasionally it clicks and since it’s typically in an area that’s been understudied, that’s why it’s so dispersed across different fields.”

Weitzman spoke proudly of his work in environmental economics, stating that he “took a decisive step in that direction a few decades ago…getting into the forefront rather than…following everything that went on.” Yet he admitted that he is not very optimistic about the current pace of efforts to combat the harmful mid- and long-term impacts of global climate change.

“It’s not merely sufficient to cut back on carbon emissions or to stabilize carbon emissions. We’ve more or less done that in the last few years, although it could go either way,” he said. “The stuff that does the damage is the stock of carbon dioxide. To get the stock of carbon dioxide to go down, it has almost nothing to do with stabilizing the flow. You have to get the flow down to net zero. That’s what’s so difficult. And the public does not realize that. Victory on the flow front doesn’t translate into victory on the stock front, and that’s what counts.”

As is typical of his style, Marty did not reveal his future plans, saying only that they remain to be determined.  But certainly all those in attendance at the symposium hope that he will continue contributing to the academic and policy discussions surrounding climate change and other critically important environmental economic issues.

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