These are excellent Nobel Prize selections, Romer for economic growth and Nordhaus for environmental economics. The two picks are brought together by the emphasis on wealth, the true nature of wealth, and how nations and societies fare at the macro level. These are two highly relevant picks. Think of Romer as having outlined the logic behind how ideas leverage productivity into ongoing spurts of growth, as for instance we have seen in Silicon Valley. Think of Nordhaus as explaining how economic growth interacts with the value of the environment. Here is their language:

2018 Sveriges Riksbank Prize in Economic Sciences is awarded jointly to William D Nordhaus “for integrating climate change into long-run macroeconomic analysis” and Paul M Romer “for integrating technological innovations into long-run macroeconomic analysis”.

Both are Americans, and both have highly innovative but also “within the mainstream” approaches. So this is a macro prize, but not for cycles, rather for growth and long-term economic prospects. Here is the Prize committee citation, always well done.

Both candidates were considered heavy favorites to win the Prize, sooner or later, and these selections cannot come as a surprise. Perhaps it is slightly surprising that they won the Prize together, though the basic logic of such a combination makes good sense. Here are previous MR mentions of Nordhaus, you can see we have been mentioning him for years in connection with the Prize.

Here is the home page of Nordhaus. Here is Wikipedia. Here is scholar.google.com. Here is Joshua Gans on Nordhaus.

Nordhaus is professor at Yale, and most of all he is known for his work on climate change models, and his connection to various concepts of “green accounting.” To the best of my knowledge, Nordhaus started working on green accounting in 1972, when he published with James Tobin (also a Laureate) “Is Growth Obsolete?“, which raised the key question of sustainability. Green accounting attempts to outline how environmental degradation can be measured against economic growth. This endeavor is not so easy, however, as environmental damage can be hard to measure and furthermore gdp is a “flow” and the environment is (often, not always) best thought of as a “stock.”

Nordhaus developed (with co-authors) the Dynamic Integrated Climate-Economy Model, a pioneering effort to develop a general approach to estimating the costs of climate change. Subsequent efforts, such as the London IPCC group, have built directly on Nordhaus’s work in this area. The EPA still uses a variant of this model. The model was based on earlier work by Nordhaus himself in the 1970s, and he refined it over time in a series of books and articles, culminating in several books in the 1990s. Here is his well-cited piece, with Mendelsohn and Shaw, on how climate change will affect global agriculture.

Nordhaus also was an early advocate of a carbon tax and furthermore note that his brother Bob wrote part of the Clean Air Act, the part that gave the government the right to regulate hitherto-unmentioned pollutants in the future. The Obama administration, in its later attempts to regulate climate, cited this provision.

I would say that much of Nordhaus’s work has its impact through being “done,” rather than through being “read.” Few economists have read through this model, which has computer programs and spreadsheets at its core. But virtually all economists read about the results of such models and have a general sense of how they work. The most common criticism of such models, by the way, is simply that their results are highly sensitive to the choice of discount rate.

In recent years, Nordhaus has shifted his emphasis to the risks from climate change, for instance in his book The Climate Casino: Risk, Uncertainty, and Economics for a Growing World. Marty Weitzman offers a good review, as does Krugman.

Assorted pieces of information on Nordhaus:

Nordhaus was briefly Provost at Yale. He also ended up being co-author on Paul Samuelson’s famous textbook in economics.

He co-authored a recent paper arguing we are not near the economic singularity; in this area his work intersects with Romer’s quite closely.

Here is a good NYT profile of Bill Nordhaus and his brother Bob, an environmental lawyer:

Bill Nordhaus, 72, a Yale economist who is seen as a leading contender for a Nobel Prize, came up with the idea of a carbon tax and effectively invented the economics of climate change. Bob, 77, a prominent Washington energy lawyer, wrote an obscure provision in the Clean Air Act of 1970 that is now the legal basis for a landmark climate change regulation, to be unveiled by the White House next month, that could close hundreds of coal-fired power plants and define President Obama’s environmental legacy.

Bob, Bill’s brother, once said: ““Growing up in New Mexico,” he said, “you’re aware of the very fragile ecosystem.””

Perhaps my personal favorite Nordhaus paper is on the returns to innovation. Don Boudreaux summarized it well:

In a recent NBER working paper – “Schumpeterian Profits in the American Economy: Theory and Measurement” – Yale economist William Nordhaus estimates that innovators capture a mere 2.2% of the total “surplus” from innovation. (The total surplus of innovation is, roughly speaking, the total value to society of innovation above the cost of producing innovations.) Nordhaus’s data are from the post-WWII period. The smallness of this figure is astounding. If it is anywhere close to being an accurate estimate, the implication is that “society” pays a paltry $2.20 for every $100 worth of welfare it enjoys from innovating activities.

There again you will see a complete intersection with the ideas of Romer. Another splendid and still-underrated paper by Nordhaus is on the economics of light. Nordhaus argues that gdp figures understate the true extent of growth, and shows that the relative price of bringing light to humans has fallen more rapidly than gdp growth figures alone might indicate. Check out this diagram. Here is a BBC summary of what Nordhaus did, in other words rates of price inflation have been lower than we thought and thus rates of real gdp growth higher.

Again, you will see Nordhaus and Romer intersecting on this key idea of economic growth.

Last but not least, Nordhaus was a pioneer on the theory of the political business cycle, namely the idea that politicians deliberately manipulate the economy, using monetary and fiscal policy, so as to boost their chances of reelection. Dare I suggest that this idea might be making a comeback?

Addendum: From Margaret Collins by email: “I’d like to call your attention to Professor Nordhaus’ longstanding association with the International Institute for Applied Systems Analysis (IIASA), the international science and policy research institution located just outside Vienna. He worked at IIASA shortly after the institute’s creation in 1972, and his work there is closely bound to the issues the Nobel Committee cites in the award — he was employed for a year in 1974-75, doing pioneering work on climate as part of IIASA’s Energy Program, and producing a working paper entitled “Can We Control Carbon Dioxide?”. That was perhaps the first economics treatment of of climate change — and Nordhaus dates his work on climate as having begun there. He has visited IIASA numerous times in the intervening years, and remains a close collaborator, particularly with Nebojsa Nakicenovic, the Institute’s Deputy Director.”

And, from the comments: “Nordhaus also helped pioneer the use of satellite imagery of night time lights as a tool for measuring economic growth, where we’ve played around with some of the publicly available tools to support various analysis.”