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.

Share

Assessing the Energy-Efficiency Gap

Global energy consumption is on a path to grow 30-50 percent over the next 25 years, bringing with it, in many countries, increased local air pollution, greenhouse gas (GHG) emissions, and oil consumption, as well as higher energy prices.  Energy-efficient technologies offer considerable promise for reducing the costs and environmental damages associated with energy use, but these technologies appear not to be used by consumers and businesses to the degree that would apparently be justified, even on the basis of their own (private) financial net benefits.

For some thirty years, there have been discussions and debates about this phenomenon among researchers and others in academia, government, non-profits, and private industry, typically couched in terms of potential explanations of the so-called “energy efficiency gap” or “energy paradox.”

Thinking About the Energy-Efficiency Gap

I wrote about this some two years ago at this blog ().  I  noted then that Professor Richard Newell of Duke University and I had just launched an initiative – sponsored by the Alfred P. Sloan Foundation — to synthesize past work on potential explanations of the energy paradox and identify key gaps in knowledge. We subsequently conducted a comprehensive review and assessment of social-science research on the adoption of energy-efficient technologies.

We worked with leading social scientists — including scholars from economics, psychology, and other disciplines, at a workshop held at Harvard — to examine the various possible explanations of the energy paradox and thereby to help identify the frontiers of knowledge on the diffusion of energy-efficient technologies.  As materials became available, we posted them at the project’s Harvard website and the project’s Duke website.

Releasing a New Monograph

I’m pleased to inform readers of this blog that we have now released a major monograph, Assessing the Energy Efficiency Gap, co-authored with Todd Gerarden, a Harvard Ph.D. student in Public Policy and a Pre-Doctoral Fellow of the Harvard Environmental Economics Program (HEEP).  The monograph draws in part from the research workshop held at Harvard (in October 2013), in which most of the U.S.-based scholars (primarily, but not exclusively, economists) then conducting research on the energy-efficiency gap participated. HEEP co-sponsored a second such research workshop with the Centre for European Economic Research (ZEW) in Mannheim, Germany in March 2014, where European economists explored the same topic. Closely-related research was presented by panelists at the annual conference of the Allied Social Science Association in January 2015.

In the new monograph, Gerarden, Newell, and I examine both the “energy paradox,” the apparent reality that some energy-efficiency technologies that would pay off for adopters are nevertheless not adopted, and the broader phenomenon we characterize as the “energy-efficiency gap,” the apparent reality that some energy-efficiency technologies that would be socially efficient are not adopted. The contrast is between private and social optimality, which ultimately has important implications for the role of various policies, as well as their expected net benefits.

Four Key Questions

We begin by decomposing cost-minimizing energy-efficiency decisions into their fundamental elements, which allows us to identify four major questions, the answers to which are germane to sorting out the causes (and reality or lack thereof) of the paradox and gap.

First, we ask whether the energy efficiency and associated pricing of products on the market are economically efficient. To answer this question, we examine the variety of energy-efficient products on the market, their energy-efficiency levels, and their pricing. Although the theory is clear, empirical evidence is—in general—quite limited. More data that could facilitate potential future empirical research are becoming available, although firm-level data are much less plentiful than data on consumers. We do not see this area as meriting high priority for future research, however, with the exception of research that evaluates the effectiveness and efficiency of existing energy-efficiency information policies and examines options for improving these policies.

Second, we ask whether energy operating costs are inefficiently priced and/or understood. Even if consumers make privately optimal decisions, energy-saving technology may diffuse more slowly than the socially optimal rate, because of negative externalities. So, even if the energy paradox is not present, the energy-efficiency gap may be. As in the first realm, the theoretical arguments are strong. Empirical evidence is considerable, and in many cases data are likely to be available for additional research. Existing policies appear not to be sufficient from an economic perspective, suggesting that further research is warranted. Indeed, we ascribe high priority to the pursuit of research in this realm.

Third, we ask whether product choices are cost-minimizing in present-value terms, or whether various market failures and/or behavioral phenomena inhibit such cost-minimization. We find that the empirical evidence ranges from strong (split incentives/agency issues and inattention/salience phenomena) to moderate (heuristic decision-making/bounded rationality, systematic risk, and option value) to weak (learning-by-using, loss aversion, myopia, and capital market failures). Importantly, here, as elsewhere in our review, the bulk of previous work has focused on the residential sector and much less attention has been given to the commercial and industrial sectors. Some areas merit priority for future research, such as empirical analysis of split incentives/agency issues in areas where efficiency standards are not present, and much more work can be done in the behavioral realm.

Fourth, we ask whether other unobserved costs may inhibit energy-efficient decisions. We find that the empirical evidence is generally sound, and that data needed for more research are available. We assign a relatively high priority to future research, particularly to aid understanding of consumer demand for product attributes that are correlated with energy efficiency, thereby informing policy and product development decisions.

Three Categories of Potential Explanations of the Gap

Finally, we ask what these findings have to say about the three categories of explanations (reviewed in detail in my 2013 essay at this blog) for the apparent underinvestment in energy-efficient technologies relative to the predictions of some engineering and economic models: (1) market failures, (2) behavioral effects, and (3) modeling flaws.  In brief, potential market-failure explanations include information problems, energy market failures, capital market failures, and innovation market failures. Potential behavioral explanations include inattentiveness and salience, myopia and short sightedness, bounded rationality and heuristic decision-making, prospect theory and reference-point phenomena, and systematically biased beliefs. Finally, potential modeling flaws include unobserved or understated costs of adoption; ignored product attributes; heterogeneity in benefits and costs of adoption across potential adopters; use of incorrect discount rates; and uncertainty, irreversibility, and option value.

It turns out that all three categories of explanations are theoretically sound and that limited empirical evidence exists for every category as well, although the empirical research is by no means consistently strong across all of the specific explanations.  The validity of each of these explanations—and the degree to which each contributes to the energy-efficiency gap—are relevant for crafting sensible policies, so Gerarden, Newell, and I hope that our new monograph can help inform both future research and policy.  Given the many energy-efficiency policies and programs that are already in place, high priority should be given to research that evaluates the effectiveness, cost-effectiveness, and overall economic efficiency of existing energy-efficiency policies, as well as options for their improvement.

Share

Thinking About the Energy-Efficiency Gap

Adoption of energy-efficient technologies could reap both private and social rewards, in the form of economic, environmental, and other social benefits from reduced energy consumption. Social benefits include improvements in air quality, reduced greenhouse-gas emissions, and increased energy security. In response, governments around the world have adopted policies to increase energy efficiency.  Still, there is a broadly held view that various barriers to the adoption of energy-efficient technologies have prevented the realization of a substantial portion of these benefits.

For some thirty years, there have been discussions and debates among researchers and others in academia, government, non-profits, and private industry regarding the so-called “energy efficiency gap” (or “energy paradox”) — the apparent reality that many energy-efficiency technologies are not adopted even when it makes sense for consumers and businesses to do so, based on their private costs and benefits. That is, decision makers appear to “under-invest” in energy-efficient technologies, relative to the predictions of some engineering and economic models.

What causes this gap?  The answer to that question could presumably help inform the development of better public policy in this realm.

Possible Explanations for the Energy-Efficiency Gap

Potential explanations for the energy efficiency gap tend to fall into three broad categories: (1) market failures, such as lack of information or misplaced incentives; (2) behavioral effects, such as inattentiveness to future energy savings when purchasing energy-consuming products; and (3) modeling flaws, such as assumptions that understate the costs or overstate the benefits of energy efficiency.  In this essay, I simply want to outline the types of hypothetical explanations of the gap that have been posited within these three broad categories.

Market-Failure Explanations

First, various Innovation Market Failures have been posited, including:  research and development (R&D) and learning-by-doing spillovers; inefficient product quality and differentiation due to market power; and inefficient introduction of new products due to consumer taste spillovers (for example, consumers becoming comfortable with a new technology).

Second, another set of potential market-failure explanations for the gap may be characterized as Information Problems.  These include:  lack of information on the part of consumers (learning-by-using or so-called experience goods; energy prices; energy consumption of products; and available substitutes); asymmetric information (the “lemons problem”); and split incentives and principal-agent issues (such as the frequently-discussed renter/owner dichotomy).

Third, there are Capital Market Failures and Liquidity Constraints, which may be a particularly significant issue in developing-country contexts.

Fourth, there are Energy Market Failures, including various externalities (environmental, energy security, congestion, and accident risk), as well as average-cost pricing of electricity.

Behavioral Explanations

The rise of behavioral economics has brought to the fore another well-defined set of potential explanations of the energy efficiency gap.  A variety of alternative taxonomies could be employed to separate these explanations, but one such taxonomy would categorize the explanations as:

Model and Measurement Explanations

The third category of possible explanations of the energy efficiency gap consists essentially of a set of reasons why observed levels of diffusion of energy-efficiency technologies may actually be privately optimal.

First, there is the possibility of unobserved or understated adoption costs, including unaccounted for product characteristics.

Second, there may be overstated benefits of adoption, due to inferior project execution relative to assumptions, and/or poor policy design.

Third, an incorrect discount rate may be employed in an analysis, when the correct consumer and firm discount rates should vary with:

  • opportunity cost of and access to capital
  • income
  • buying versus retrofitting equipment
  • systematic risk
  • option value (see below)

Fourth, there is frequently heterogeneity across end users in the benefits and costs of employing energy-efficiency technologies, so that what is privately optimal on average will not be privately optimal for all.  This can refer either to static (cross-sectional) heterogeneity or to dynamic (intertemporal) heterogeneity, that is, technology improvements over time, which raises two possibilities:  the reality of some potential adopters being short of the frontier, and the presence of option value to waiting.

Fifth and finally, there is the possibility of uncertainty (real, not informational, as above), irreversibility, and option value.  This could be due to uncertainty regarding future energy prices, or can be linked with option value that arises for delaying investments that have only minimal if any salvage value.

Public Policy and Next Steps

Determining the validity of each of these possible explanations — and the degree to which each contributes to the energy efficiency gap — are crucial steps in crafting the most appropriate public policy responses.

To inform future research and policy, Professor Richard Newell of Duke University and I have launched an initiative – sponsored by the Alfred P. Sloan Foundation — to synthesize past work on these potential explanations of the energy paradox and identify key gaps in knowledge.  We are conducting a comprehensive review and assessment of published and ongoing social-science research on the adoption of energy-efficient technologies, including scholarly literature, industry case studies, reports from national and sub-national governments, and, to the extent possible, consulting reports evaluating specific programs.

We are working with leading social scientists — including scholars from economics, psychology, and other disciplines — to examine the various possible explanations of the energy paradox and thereby to help identify the frontiers of knowledge on the diffusion of energy-efficient technologies.  We hope the products of this initiative will help decision makers in industry and government better understand the energy efficiency gap, and will thereby contribute to decisions that maximize the potential economic, environmental, and other social benefits associated with optimal adoption of energy-efficient technologies.  As materials become available, we will post them at the project’s Harvard website and the project’s Duke website, and I will alert readers of this blog.  In the meantime, please stay tuned.

Share