An Economic View of the Environment - Page 31 of 76 - One Economist's Perspective on Climate and Other Policy

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 27^th, 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.

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 20^th 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.

Sub-National Climate Change Policy in China

At a time when there are considerable political challenges in some countries (such as my own!) for national governments to institute meaningful climate change policies, the potential role of sub-national policies becomes more important than otherwise. In other countries, sub-national climate policies may be a stepping stone to significant national efforts, as in China. Partly with this in mind, the Harvard Project on Climate Agreements (HPCA) conducted a research workshop in July of this year on “Sub-National Climate Change Policy in China.” Tsinghua University’s Institute of Energy, Environment, and Economy — directed by Professor Zhang Xiliang — hosted and co-sponsored the workshop, which was organized by my colleague at the Harvard Kennedy School, Dr. Robert Stowe. Twenty-seven experts from China, Europe, Canada, India, Australia, and the United States participated (see the photo below). In addition, a group of students observed the workshop, and the Environmental Defense Fund’s China Program hosted a dinner for workshop participants. The Harvard Global Institute provided major support for the project. Here is a link to the full agenda (in both Chinese and English).

Background

Climate change is a global commons problem, and, as such, requires cooperation at the highest jurisdictional level — that is, international cooperation among national governments — if it is to be adequately addressed. Participation by national governments is key, and sub-national governments can also play important roles. Provinces and municipalities around the world have undertaken initiatives — sometimes working together across national boundaries — to reduce greenhouse-gas emissions. These include jurisdictions in the largest-emitting countries — China, the United States, and India — as well as in the European Union.

The Workshop and its Analyses

Participants in the Beijing workshop examined how Chinese provinces and municipalities work with the central government to implement policy — and discussed challenges to such cooperation. They focused to a considerable degree on the implementation of China’s national carbon-pricing system, including approaches to integrating the seven pilot sub-national market-based systems into the new national scheme, scheduled to launch in 2020 (see “What Should We Make of China’s Announcement of a National CO₂ Trading System?,” January 7, 2018). Participants also addressed sub-national dimensions of other policy approaches to reducing greenhouse-gas emissions in China.

As we have done with previous HPCA research and policy workshops, participants in the Beijing event are now writing briefs on topics related to their respective presentations. We will edit and compile these short papers in a volume to be released later this year. In the meantime, you can view the PowerPoint presentations from the Beijing workshop:

China’s National Emissions Trading Program (Zhang Xiliang)
Ten Drivers Behind Climate Policy Making in China (Qi Ye)
Creating Sub-National Climate Institutions in China (Michael Davidson)
Multi-Dimension Post-Assessment of China’s ETS Pilots (Qi Shaozhou)
Political Economy Framework for Climate Change Policy in China (Christine Wong)
Canadian Climate Change Policy (Katie Sullivan)
Sub-National Carbon-Pricing Policy in the USA (Robert Stavins)
Integration of China’s National ETS with Provincial/Municipal Pilots (Valerie Karplus)
Introduction of Beijing ETS (Mei Dewen)
Sub-National Implementation Pathways for the National Pricing System (Goerild Heggelund)
Assessing Regional Implementation Pathways of National ETS In China (Wu Libo)

The Larger Context

The Beijing workshop was part of a larger initiative of the Harvard Project on Climate Agreements, supported by the Harvard Global Institute, examining and comparing sub-national climate-change policies in China and India. We will conduct a similar workshop in New Delhi next year.

The Harvard Project has previously conducted three workshops addressing climate-change policy in — or related to — China:

“Bilateral Cooperation between China and the United States: Facilitating Progress on Climate-Change Policy,” June 2015. This was hosted by China’s National Center for Climate Change Strategy and International Cooperation (NCSC). You can read more about this workshop here, and read the full workshop report here.
“The Design, Implementation, and Operation of China’s National Emissions Trading System,” December 2016. Our host was NCSC. The participants explored technical issues related to the design of China’s emerging national system, including allowance allocation, point of regulation, and price management.
“Cooperation in East Asia to Address Climate Change,” September 2017. This was hosted by the Harvard Center Shanghai, and supported by the Harvard Global Institute. You can read more about the workshop here, and read the complete volume of briefs based on the workshop here.

The Future of U.S. Carbon-Pricing Policy

In 2007, I was asked by the leaders of the Brookings Institution’s Hamilton Project to write a paper describing a national emissions trading system to reduce U.S. carbon dioxide (CO₂) emissions to help address the threat of global climate change. I responded that I would prefer to write broadly about carbon-pricing instruments, including what I considered to be the symmetric instruments of a carbon tax and a carbon trading program. But the Hamilton Project leaders said no, they would find someone else to write about carbon taxes (which turned out to be Gib Metcalf), and they wanted me to “make the strongest case possible for” what is today called a cap-and-trade system. I did my best, and in the process I came to be identified – and to some degree may have become – an advocate for CO₂ cap-and-trade. For better or for worse, during the Obama administration transition, the design recommendations in my Hamilton Project paper became one of the starting points for efforts to structure the administration’s proposed CO₂ cap-and-trade system that became part of the failed Waxman-Markey legislation, H.R. 2454, the American Clean Energy and Security Act of 2009.

More than a decade later, I have written a new paper in which I seek to approach this question as I wished to in the first place, treating both instruments in a balanced manner, examining their merits and challenges, without necessarily favoring one or the other. On May 16, 2019, I presented this new paper at the National Bureau of Economic Research’s first annual Environmental and Energy Policy and the Economy Conference, held at the National Press Club in Washington, D.C. My topic was, “The Future of U.S. Carbon-Pricing Policy.” (It will be forthcoming in Environmental and Energy Policy and the Economy, volume 1, edited by Matthew Kotchen, James Stock, and Catherine Wolfram, published by the University of Chicago Press.) In today’s blog essay, I provide a very brief summary of the paper, based upon the presentation I made at the NBER conference. I hope you will find this of sufficient interest to download and read the complete paper.

Premises, Questions, and Conclusions

I began this research with two major premises: first, that economists and most other policy analysts agree that carbon-pricing will likely be a necessary (although not sufficient) part of any meaningful, long term U.S. climate change policy, because of: (1) feasibility – the necessity of affecting millions, indeed hundreds of millions, of decentralized decisions; (2) cost-effectiveness, given the tremendous heterogeneity of marginal abatement costs; and (3) the importance of providing incentives for carbon-friendly technological change. My second premise was that there is much less agreement among economists (and other policy analysts) regarding the choice of specific carbon-pricing policy instrument – carbon tax or cap-and-trade.

This prompts two questions: (1) how do the two major approaches to carbon pricing compare on relevant dimensions, including but not limited to efficiency, cost-effectiveness, and distributional equity? (2) Which approach is more likely to be adopted in the future in the United States?

Having carried out an exhaustive examination, two major conclusions stand out (among others). First, that the specific designs of carbon taxes and cap-and-trade are more consequential than the choice between the two instruments. And second, that political feasibility affects the normative merits of the two instruments, and vice versa.

Similarities & Symmetries

Of fourteen separate issues I examine, some appear at first to be key differences (in theory), but many of these differences fade on closer inspection, and depend on specifics of design.

First of all, carbon taxes and commensurate cap-and-trade turn out to be perfectly equivalent in regard to: (a) incentives for emission reduction (both can be upstream on the carbon content of fossil fuels); (b) aggregate abatement costs (both can be cost-effective, both provide the same incentives for technological change, and both can utilize offsets to further lower aggregate abatement costs); and (c) effects on competitiveness (both can lessen these impacts via appropriate border adjustment mechanisms).

Next, the two instruments are nearly equivalent in regard to possibilities for raising revenue (cap-and-trade can utilize auctions, but given the structure of Congressional committees, revenue recycling may be easier with taxes).

And these instruments are similar in regard to: (a) costs to regulated firms (cap-and-trade systems can freely allocate allowances, and taxes can provide inframarginal exemptions below a specified level of emissions); and (b) distributional impacts (the two instruments can be designed to be roughly equivalent in this regard).

Differences & Distinctions

Beginning with the least significant differences, there are relatively minor distinctions in terms of transaction costs (decreasing marginal transaction costs in cap-and-trade systems – such as with volume discounts on brokers’ fees – can violate the independence property, whereby the equilibrium allocation of allowances and hence aggregate costs are ordinarily independent of the initial allocation).

There are more meaningful, but still subtle differences with regard to: (a) performance in the presence of uncertainty (for this, I urge you to read at least this section of the complete paper, because new research suggests that the implications of the classic Weitzman rule in the presence of a stock externality are moderated – if not reversed – due to the persistent effects of technology shocks, which foster positive correlation between marginal benefits and marginal costs); and (b) linkage with other jurisdictions (it is easier with cap-and-trade systems, but tax systems can also be linked).

That said, there are significant differences between the instruments in terms of: (a) carbon-price volatility (a problem only with cap-and-trade systems, but a problem that can be mitigated with price collars and banking of allowances); (b) interactions with complementary policies (a significant issue with cap-and-trade systems, which is much less severe with carbon taxes, because the “waterbed effect” is eliminated); (c) market manipulation (there is a need for regulatory oversight in cap-and-trade systems, but tax evasion is a parallel issue in tax systems, although presumably less severe in the U.S. context); and (d) complexity and administrative requirements (cap-and-trade is certainly more complex and has greater administrative requirements, but one might ask whether a simple tax will remain “simple” as it works its way through the Congress).

Hybrid Policy Instruments and a Policy Continuum

Many of the remaining differences can diminish further with implementation. Indeed, hybrid policies which mix features of tax and cap-and-trade blur distinctions. For example, auctioning of allowances and the use of price collars bring cap-and-trade closer to a tax system; and quantity formula employed to adjust a tax, and the use of tax revenues to mitigate emissions bring a tax closer to cap-and-trade. The result is that the dichotomous choice between a carbon tax and cap-and-trade can become a choice of design elements along a policy continuum, and the design of these instruments can be more consequential than the choice between the two.

Which is More Likely to be Adopted – Taxes or Trading? Positive Political Theory

Framing this question in terms of the metaphor of a political market, it is helpful to think about political demand and political supply of policy instruments. In terms of the demand from interest groups, first, regulated industry may oppose an ordinary tax approach, as it typically leads to greater costs than the simplest cap-and-trade (or than a performance standard, for that matter), because private industry is paying not only for compliance costs, but also for the tax on residual emissions. Second, regulated industry may favor cap-and-trade, because it conveys scarcity rents to firms, and can provide entry barriers for potential new entrants, which can make the rents sustainable.

Environmental advocacy groups favor cap-and-trade, due to the emissions certainty it provides, but also because presumably they have a preference for policies that help obscure costs, and cap-and-trade does a better job of sweeping discussion of costs under the rug than does a tax. However, in the era since cap-and-trade was demonized as “cap-and-tax,” this difference may be much less than it was!

Turning to the supply side (within the legislature), the revenue from either a tax or auctioning of allowances can be attractive to government. And because of the independence property of cap-and-trade, legislators can allocate allowances to build political support without increasing the costs or reducing the effectiveness of the policy. Of course, this important political advantage becomes an economic disadvantage if it invites particularly harmful rent-seeking behavior. Finally, environmental policy makers tend to think in terms of pollution quantities, not prices.

Experience with Carbon Pricing: Emissions Coverage & Price in Implemented Initiatives

There are some fifty carbon-pricing systems in operation worldwide, with equal numbers of carbon taxes and carbon cap-and-trade systems. A quick comparison of these policies reveals two striking realities. First, the highest carbon prices (the height of the bars in the figure below) are for carbon taxes (in norther Europe). Second, the scope of coverage (the width of each bar in the figure) of cap-and-trade systems greatly exceeds that of carbon taxes. Putting the two features (severity and scope) together, a reasonable measure of the relative importance of the policies is given by multiplying the carbon price (tax level or market price of allowances) by the tons of coverage, that is, the respective areas in the figure. On this basis, it appears that political revealed preference has been weighted toward cap-and-trade (at least up until now).

Carbon Price & Emissions Coverage of Implemented Carbon-Pricing Initiatives

Which Has Worked Better – Experiences with Trading and Taxes

Based upon more than thirty years of experience with cap-and-trade systems, including but not limited to CO₂ programs, lessons regarding the design and efficacy of these systems can be drawn. In brief, there is empirical evidence for the following: cap-and-trade has proven to be environmentally effective and economically cost-effective; downstream, sectoral programs have been common, but economy-wide upstream systems are feasible; transaction costs have been low to trivial; a robust market requires a cap below business-as-usual; banking has been exceptionally important, representing a large share of the gains from trade; price collars are very beneficial; free allocation of allowances fosters political support, with a likely transition to greater auctioning over time; competitiveness impacts can be mitigated with an output-based updating allocation; “complementary policies” are common, but in some cases can have perverse consequences, including no additional emissions reduction, an increase in aggregate costs, and suppressed allowance prices.

Turning to experiences with carbon taxes, two applications stand out. First, there are the northern European carbon tax systems, initiated in the 1990s in Norway, Sweden, Denmark, and Finland. Typically these were elements of broader energy and excise tax reform initiatives, and some are at the highest levels of any carbon-pricing regimes worldwide. However, fiscal cushioning has been common for industries expressing concerns. That said, these taxes have raised significant revenues to finance spending or to lower other tax rates, but unfortunately, there is little empirical evidence of their emissions impacts.

More striking is British Columbia’s carbon tax, initiated in 2008, which comes closest to that recommended by economists. Currently, it is an upstream tax of $27/ton of CO₂, but with important exemptions in place for key industries. Importantly, 100% of tax revenue was originally refunded through general tax rate cuts, but over time, there has been more focus on tax cuts for specific sectors and locations. Although there is some debate in the literature, it appears to have been effective in reducing emissions.

Empirical Evidence for Positive Assessment

Given that the normative differences between the two instruments are minimal, a key question becomes which instrument is more politically feasible, and which is more likely — in practice — to be well designed. Based on experiences with cap-and-trade and carbon taxes, the relative masses in the figure above suggest that political revealed preference has favored the former. Furthermore, after years of deliberation, China has chosen trading for its national program (although it appears to be a set of sectoral tradable performance standards, not a true, mass-based cap-and-trade system). In addition, the new “Transportation and Climate Initiative” in the northeast United States was first proposed in terms of fuel taxes but is gravitating toward cap-and-trade. Also, New Jersey is preparing to rejoin the Regional Greenhouse Gas Initiative, and Oregon is poised to enact an economy-wide CO₂ cap-and-trade system this year. On the other hand, Washington State has twice defeated a carbon tax.

But past may not be prologue. The demonization of the Waxman-Markey trading system as “cap-and-tax” may have reduced the political advantage of cap-and-trade (that it can hide the costs). And there is clearly increasing interest in a national carbon tax in the policy world, including several bills in Congress and the prominent Climate Leadership Council proposal. On the other hand, the “Green New Deal” is silent about carbon-pricing of any kind.

It is worthwhile focusing on the political economy of the British Columbia carbon tax. Its successful enactment has been attributed to “the confluence of political conditions ripe for carbon taxation”: untapped hydroelectric potential; a strongly environmentalist electorate (as in the case of California’s move to cap-and-trade with Assembly Bill 32); a right-center government with trust from the business community (as with the George H.W. Bush administration’s SO₂ allowance trading system in the Clean Air Act amendments of 1990); and a premier with institutional capacity to pursue personal policy preferences. There has been increasing public support over time, due to the perception of emissions reductions without severe economic impacts, but political pressures have caused the evolution of the system from using revenues exclusively to cut distortionary taxes to greater use of tax cuts to favor specific sectors and regions.

Clearly, political pressures can drive up social costs with either type of carbon-pricing instrument. On the one hand, politics may disfavor the auctioning of allowances in cap-and-trade systems, while, on the other hand, politics may disfavor cost-effective cuts of distortionary taxes in tax systems.

Does Either Carbon-Pricing Instrument Dominate in Normative or Positive Terms?

When carbon taxes and cap-and-trade are designed to be truly comparable, their characteristics and outcomes are similar, and in some cases fully equivalent (normatively), in terms of their: emission reductions, abatement costs, revenue raising, costs to regulated firms, distributional impacts, and competitiveness effects. But on some other dimensions, there can be real differences in performance. The tax approach is favored by administrative requirements, interactions with complementary policies, and effects on carbon-price volatility; whereas cap-and-trade is favored by linkage with policies in other jurisdictions, and possibly by anticipated performance in the presence of uncertainty. In the positive political economy domain, the evidence is also decidedly mixed. Hence, there is not a strong case for the blanket superiority of either instrument. Differences in design simply dominate differences between the instruments themselves.

Can Carbon-Pricing be Made More Politically Acceptable?

The track record of 50 carbon-pricing policies cited above should be contrasted with the 176 countries with renewable energy policies or energy efficiency standards, as well as another 110 national and sub-national jurisdictions with feed-in tariffs. Hence, carbon pricing has not in general been the favored approach to climate change policy. Why is this the case? Survey and other evidence indicates that public perceptions – some of which are inaccurate – are primary factors behind aversion to carbon taxes: “personal costs too great; policy is regressive; could damage economy; will not discourage carbon-intensive behavior; and government just want the revenues.” So, one way to improve public acceptance could be through better information, that is, education.

But another way forward could be through judicious policy design, which may well depart from first-best design, including: phasing in taxes/caps over time (which was effective in California and British Columbia); earmarking revenues from taxes/auctions to finance additional climate mitigation, in contrast with optimizing the system via cuts in distortionary taxes; and/or using revenues for fairness purposes, such as with lump-sum rebates or rebates targeted to low-income and other particularly burdened constituencies (a carbon tax with “carbon dividends” or a cap-and-trade system in the form of “cap-and-dividend”).

Has the Defeat of National CO₂ Cap-and-Trade Initiatives Provided Openings for Carbon Tax Proposals?

Political polarization has decimated the key source of Congressional support for environmental/energy action, the political middle. And the successful political battle against the Obama administration’s CO₂ cap-and-trade legislation featured the effective demonization of that instrument as “cap-and-tax.” Does the consequent reputational loss for cap-and-trade provide a meaningful opening for the other carbon-pricing instrument – a carbon tax?

It would seem that large budgetary deficits ought to increase the attraction of new sources of revenue, but existing carbon tax proposals have largely been revenue-neutral. That said, it is surely true that there has been increased attention to carbon taxes from the “policy community,” with support coming not just from Democrats, but also from prominent Republican academic economists and former Republican high government officials. But – finally – what about in the real political world of those currently holding elective office in the federal government?

It is presumably good news for carbon tax proposals that they are not “cap-and-trade.” Perhaps that helps with the political messaging. But if conservative opposition could tarnish cap-and-trade as “cap-and-tax,” surely it will not be difficult to label a tax as a tax! And in addition to such opposition from the political right, it is – as of now – questionable whether the new left will want a carbon tax to be part of its “Green New Deal.”

Hence, in the short term, national carbon pricing of either type will likely continue to face an uphill battle. Therefore, in addition to considering second-best carbon-pricing design (as I recommended above), economists can work productively to catch up with political realities by considering better designs of second-best non-pricing instruments, such as clean energy standards.

But, at some point the politics will change, and it is important to be ready, which is why – for the longer term – ongoing research on carbon-pricing is very much warranted, particularly if it can be carried out in the context of real-world politics, and focus on policies that are likely at some point to prove feasible.