The Nobel Memorial Prize for William D. Nordhaus

William D. Nordhaus and Paul M. Romer received the 2018 Sveriges Riksbank Prize in Economic Sciences in Memory of Alfred Nobel. This paper surveys Nordhaus’ contributions on “integrating climate change into long‐run macroeconomic analysis”, for which he was recognized with this Prize.     

Paul Romer: Ideas,Nonrivalry, and Endogenous Growth

In 2018, Paul Romer and William Nordhaus shared the Sveriges Riksbank Prize in Economic Sciences in Memory of Alfred Nobel. Romer was recognized “for integrating technological innovations into long‐run macroeconomic analysis”. This article reviews his prize‐winning contributions. Romer, together with others, rejuvenated the field of economic growth. He developed the theory of endogenous technological change, in which the search for new ideas by profit‐maximizing entrepreneurs and researchers is at the heart of economic growth. Underlying this theory, he pinpointed that the nonrivalry of ideas is ultimately responsible for the rise in living standards over time.     

Variety of products,public capital,and endogenous growth

This paper develops an extension of the endogenous growth model with variety expansion presented in Romer [Romer, P.M., 1990. Endogenous technical change, Journal of Political Economy 98, part 2, S71–S102] by considering public capital accumulation. Characterizing the transitional dynamics, the growth rate of consumption traces (and available number of intermediate goods also might trace) an S-shaped converging path to the equilibrium growth rate, similar to a logistic growth curve, if the intensity of public capital is sufficiently high. We also show that public investment enhances economic growth because it stimulates demand for intermediate goods and raises the market interest rate.     

The impact of personal beliefs on climate change: the “battle of perspectives” revisited

The paper proposes a multi-agent climate-economic model, the “battle of perspectives 2.0”. It is an updated and improved version of the original “battle of perspectives” model, described in Janssen (1996) and Janssen/de Vries (1998). The model integrates agents with differing beliefs about economic growth and the sensitivity of the climate system and places them in environments corresponding or non-corresponding to their beliefs. In a second step, different agent types are ruling the world conjointly. Using a learning procedure based on some operators known from Genetic Algorithms, the model shows how they adapt wrong beliefs over time. It is thus an evolutionary model of climate protection decisions. The paper argues that such models may help in analyzing why cost-minimizing protection paths, derived from integrated assessment models à la Nordhaus/Sztorc (2013), are not followed. Although this view is supported by numerous authors, few such models exist. With the “battle of perspectives 2.0” the paper offers a contribution to their development. Compared to the former version, more agent types are considered and more aspects have been endogenized.     

No matter how it is measured, income declines with global warming

The contemporaneous relationship between temperature and income is important because it enables economists to estimate the economic impact of global warming without assuming a structural model. Until recently, empirical evidence generally suggests that there is a negative relationship between temperature and income, and, therefore, global warming has an adverse impact on economic activity. However, Nordhaus (2006) argues that the temperature-income relationship depends on how income is measured. We show in this paper that the results of Nordhaus (2006) may be due to an omitted-variable problem. Based on a well-motivated temperature-income model, we find that the relationship between temperature and income is not dependent on income measurement. Our regression results show that the adverse impact of an increase of 1 °C in temperature can be as much as a 3% decrease in total income for the G-7 nations. Therefore, our results suggest an aggressive climate mitigation policy.     

Time Preference, Stock Externalities and Strategic Reactions

This paper examines the relationship between the rateof time preference and strategic reactions in dealing with climate change caused by anthropogenic greenhouse gas (GHG) emissions. Treating climate change as stock externalities, the RICE model (Nordhaus and Yang [1996]) is employed in this paper for simulation studies. The simulation results show that when regions' rate of time preference in evaluating climatechange is sufficiently low, the paths of efficient GHGemission reduction measurement and the inefficient Nash equilibrium outcome are close. The paper also provides general interpretations of such phenomena. Finally, the implications of a low rate of time preference on GHG emission reduction policies are discussed.     

Growth,R&D,and uncertainty

I develop and analytically solve the stochastic Romer model in which the creation of ideas is driven by a stochastic process. I show that higher uncertainty about R&D, through the reallocation effects of resources among sectors, slows down economic growth and deteriorates welfare. The results suggest that persistently high uncertainty tends to severely restrict the scope of sustained income growth.     

Multiple steady states,indeterminacy, and cycles in a basic model of endogenous growth

The goal of this paper is to demonstrate that a basic model of endogenous growth with learning by doing may produce a rich array of outcomes. Starting point of our analysis is the Romer (1986a) approach. In contrast to Romer, however, we assume that one unit of investment shows different effects concerning the building up of physical and human capital, so that these variables cannot be merged into one single variable. With this assumption, it can be shown that multiple steady states, indeterminacy of equilibria, and persistent cycles may result in our model.     

Endogenous Land use and the Ricardian Valuation of Climate Change

The Ricardian technique uses cross-sectional variation in the capitalized value of climate in land to infer the agricultural costs or benefits of dynamic climate change. While a practical approach for predicting the consequences of global warming with readily available data, it may yield biased results when land-use decisions depend on the climate attributes being valued and when land has unobserved attributes that differ with the use to which it is put. This paper illustrates the conditions under which such a bias will occur, describes an empirical model that corrects for it, and estimates that model with agricultural census data from Brazil. The approach, moreover, allows constraints on adjustment to be explicitly incorporated into the Ricardian framework, relaxing one of that technique’s most conspicuous assumptions. I would like to thank Patrick Bayer, Steven Berry, Robert Evenson, Michael Hanemann, Robert Mendelsohn, Bill Nordhaus, Kerry Smith, Karl Storchmann, two anonymous referees, and seminar participants at the University of California – Santa Barbara and the Research Triangle Institute for their useful insights and helpful comments. All remaining errors and omissions are my own. Fabiana Tito provided excellent research assistance, and Denisard Alves and Robert Evenson generously supplied the data.     

Economic growth, skill-biased technical change and wage inequality: A model and estimations for the US and Europe

In recent literature skill-biased technical change has been viewed as a major cause for wage inequality. Some modelling and presentation of stylized facts have been undertaken for US time series data. A preliminary study of wage inequality in a model with knowledge as input in an aggregate production function has been presented by Riddell and Romer [General Purpose Technologies and Economic Growth, 1998, MIT Press]. Although some important forces determining wage inequality are widely accepted we know little about the quantitative impact of each source and differences across countries. We present a growth model of the Romer type with innovation-based technical change and two skill groups where the growth of knowledge, the relative supply of the two skill groups, externalities and substitution effects among the two groups are the driving forces for wage inequality. We undertake estimates for US time series data and contrast those estimates with results from some European countries. In particular, we compare parameter estimations for US and German time series data. The paper concludes that there is less wage inequality across skills in Europe in contrast to the US on the macroeconomic level. But, considering disaggregated data we observe some increases in inequality for Germany, too. Although our model reveals important variables for the explanation of wage inequality there may, however, also be other factors, such as trade unions, which have impacted the wage spread.     

教育、创新与经济增长

由于知识的非竞争性,基于R&D的内生增长模型存在规模效应,即人口数量越大,从事R&D的人员越多,经济增长率越快。本文将R&D人员创新活动的有效时间引入知识的积累方程———“点子”生产函数,发现OECD国家科学家和工程师数量增加伴随着R&D人员创新活动的有效时间的减少,二者相互抵消,使得TFP增长率保持不变。通过校准理论模型,本文模拟了49个国家的经济增长率,发现模型对经济增长率跨国数据的解释能力明显强于Lucas模型和Romer模型。如果利用模型对跨国经济增长率的模拟值与真实值之间的残差平方和来评判模型的优劣,则本文模型对Lucas模型和Romer模型至少分别改进了20%和59%。     

Tax multipliers and monetary policy: Evidence from a threshold model

Romer and Romer (2010) use the narrative record to generate a time series of exogenous shocks to fiscal policy. They report a tax multiplier of 3.0. We extend their analysis and allow for nonlinearities between their shocks and the effects on output by estimating a threshold regression model. Using Hansen’s (1997) procedure, we find the best fitting threshold is changes in the federal fund rate with a delay of two quarters. Moreover, we find that the tax multiplier is approximately 4.3 if accompanied by an accommodative monetary policy and approximately 1.2 under tight monetary policy.     

Dynamical analysis of the R&D-based growth model with a regime switch

Several empirical studies suggest that advanced economies experience a growth regime switch from factor accumulation to knowledge accumulation. To investigate the mechanism of such a regime switch, this study develops a concise and flexible dynamic model based on Romer (J Polit Econ 98:S71–S102, 1990) by introducing two types of endogenously supplied R&D input capital. The model replicates the growth patterns of developed and underdeveloped nations, clarifies the important role that capital plays in the difference between them, and presents several implications for interest-rate subsidies and official development assistance. Further, it shows that if a country enjoying long-run growth has little initial capital, its initial economic development will be based on capital accumulation. When the capital stock becomes sufficient for supporting R&D, the economy will achieve long-run growth through R&D.     

Strategic policies and growth: an applied model of R&D-driven endogenous growth

We introduce and explore a general equilibrium model with R&D-driven endogenous growth, whose antecedents are the models of Romer (1990) [Romer, P.M., 1990. Endogenous technological change. Journal of Political Economy, 98, S71-102] and Grossman and Helpman (1991) [Grossman, G.M., Helpman E., 1991. Innovation and Growth in the Global Economy, The MIT Press, Cambridge]. Utilizing evidence from recent econometric studies on sources of growth, the model also accounts explicitly for cross-border technological spillovers. The model is specified and calibrated to data from Japan, and is solved to obtain both the transitional and the steady-state equilibria. We explore the effects of selective trade and R&D promotion policies on long-run growth and social welfare. The model results suggest that while a strategic trade policy has little effect on re-allocating resources into domestic R&D activities, it can significantly affect the cross-border spillovers of technological knowledge, which, in turn, stimulates growth. We find that trade liberalization may cause the growth rate to fall and lead to a loss of social welfare in the long-run, although it improves welfare in the short-run. R&D promotion policies stimulate growth by inducing private agents to allocate more resources to domestic R&D, as well as to take greater advantage of global R&D spillovers. Here, we find significantly high growth effects together with sizable gains in social welfare at low incidence to tax payers.     

A “Managerial” trade union and economic growth

By setting up a simple Romer-type [Romer, P.M., 1989. Capital accumulation in the theory of long-run growth. In: Barro, R.J. (Ed.), Modern Business Cycle Theory. Harvard University Press, Cambridge, MA] endogenous growth model embodying a political trade union (rather than the traditional economic labor union), this paper explores the effects of unionization on unemployment, growth and welfare by highlighting the essence of internal conflict within the union. It is shown that the conflicting interests between the leadership and membership within the union play a decisive role in the unemployment, growth and welfare effects of unionization. Given the fact that taxation is another potential candidate besides unions in explaining the poor performance of a macro-economy, we re-examine the taxation effects within the growth model with equilibrium unemployment caused by the presence of the trade union and compare our findings with those for the traditional full-employment growth model. In general, we find that the taxation effects of income and consumption crucially depend not only on the institutional arrangements for taxing unemployment benefits, but also on the way the government budget is balanced.     

Political and Legal Factors of Economic Growth in Russian Regions

The authors propose some new approaches in order to evaluate formally regional specifics of political and legal culture and institutes' impact on the dynamics of economic development of the regions and on the regions' investment climate. They demonstrate using a model that the influence of institutional factors, including some indicators for the basic individual rights maintenance in the regions, on economic growth is significant.     

The impact of knowledge accumulation and geographical spillovers on productivity and efficiency: The case of U. S. shipbuilding during WWII

This paper examines the productivity and efficiency experience of World War II Liberty ship builders using two complementary paradigms which can be viewed as alternative specifications of the endogenous growth model introduced by Romer (1986) and the stochastic frontier production model introduced by Aigner, Lovell, and Schmidt (1977). We develop modifications in the endogenous growth model to allow for learning as well as spatial spillovers by relating productivity growth to cumulative productive experience (the ‘learning curve’) and to worker experience as it is transferred and utilized across different geographical regions. We also consider the relative impact of both proximal and distant simultaneous production on productivity growth. We then utilize a framework in which the efficiency component of productivity growth is explicitly considered using a stochastic frontier model wherein contributions to productivity growth introduced in the endogenous growth model are formally modeled as determinants of efficiency change.     

A Ricardian model of climate change in Canada

Abstract A comparative static 'Ricardian' model is used to establish relationships between climate and agricultural land value in Canada. From these relationships, agricultural costs of climate change scenarios are estimated. This study is motivated partly by evidence of potential agricultural benefits of climate change from a similar analysis of the United States by Mendelsohn, Nordhaus and Shaw, and partly by the void of Canadian studies. Furthermore, it extends the analysis to non‐uniform climate change scenarios. Its finding of a slightly positive upper bound on the agricultural benefits from climate change, within a wide margin of error, is motivation for further analysis.
Un modèle ricardien de changement climatique au Canada.  L'auteur utilise un modèle statique ricardien classique pour établir des relations entre le climat et la valeur des terres agricoles au Canada. A partir de ces relations, on calibre les coûts agricoles de divers scénarios de changement climatique. Cette étude a pris forme en partie en réaction aux résultats d'une analyse similaire de Mendelsohn, Nordhaus et Shaw aux Etats‐Unis, et en partie en réponse à un manque d'études de ce genre au Canada. Cet article étend les analyses aux scénarios de changements climatiques non‐uniformes. Les résultats suggèrent qu'il existe une sorte de borne positive supérieure aux avantages agricoles du changement climatique, à l'intérieur d'une marge d'erreur assez vaste. Voilà qui encourage à poursuivre les analyses.     

ROLLING DICE FOR THE FUTURE OF THE PLANET

In an influential paper published in Science, Nordhaus employs an integrated climate-economy model to study climate change. He finds that optimizing climate change policy requires low levels of controls on emissions of greenhouse gases. This paper follows his pioneering methodology but challenges his conclusions. Nordhaus's results depend crucially on certain parameters such as the discount rate and the autonomous decline in energy intensity of production. However, choosing a set of different though equally plausible values for these parameters causes the control rate to rise substantially. This translates into a greater level of action for slowing climate change.     

Reassessing the empirical validity of the human-capital augmented neoclassical growth model

We reassess Mankiw, Romer and Weil's [mrw] version of the Solow model using, as did mrw, cross-sectional data to estimate the steady-state equation governing income per capita levels. The model fails in two critical areas. First, plausible factor shares obtained by mrw are not robust to the substitution of two measures of human capital that are more precise than the secondary school enrollment rates used by mrw. Second, the null hypothesis of an exogenous and identical level of technology in all countries is rejected. We also explain why the Solow model performed well despite the above shortcomings.