This paper analyzes the relationship between the expectational stability of rational expectations solutions and the possible convergence of adaptive learning processes. Both concepts are used as selection criteria in the case of multiple rational expectations solutions. Results obtained using recursive least squares lead to the conjecture that there exists a general one-to-one correspondence between these two selection criteria. On the basis of a simple linear model and a stochastic gradient algorithm as an alternative learning procedure, it is demonstrated that such a conjecture would be incorrect: There are cases in which stochastic gradient learning converges to rational expectations solutions that are not expectationally stable.

This paper builds a macroeconomic model of equilibrium unemployment in which firms persistently face difficulties in selling their production, and this affects their decisions to create jobs. We show that the competitive search equilibrium is not efficient and that inflation is detrimental to unemployment.

Discrete-time and continuous-time models with time to build do not possess the same dimension. In this paper we address the dimensionality issue by revising the way time to build is traditionally measured when transforming the economic dynamics from discrete to continuous time. We propose our new procedure as an alternative approach which allows for a unifying theory of the two classes of economic growth models. Interestingly enough, discrete-time models admit a change in stability for a value of the time-to-build parameter where their continuous counterpart admits an Hopf bifurcation.

We develop a dynamic general equilibrium growth model, where households purchase final goods on cash or credit and have different capital and money endowments, to investigate whether inflation affects trends in income and consumption inequality. We show that, under a strong substitutability between cash and credit goods, inflation has a negative relationship with income inequality, but a U-shaped relationship with consumption inequality. The divergence between income and consumption inequality explains several recent empirical observations. This result has important policy implications, as consumption inequality better reflects the welfare distribution whereas income inequality fails to capture consumption disparities resulting from different consumption and asset distributions across households. In the growth model with heterogeneous households, there is a mixed relationship between growth and income inequality, confirming the existence of the Kuznets curve. The inflation-driven asset reallocation might also produce a Mundell–Tobin effect, enhancing growth.

In this paper, the location patterns of Multinational Enterprises are modeled by an evolutionary two-country model in which producing in a developed economy offers strong cost-reducing externalities of within-country spillovers and opting for a developing economy entails cheap labor but also extra operational costs due to the undersupply of public goods. The offshoring process, that is, manufacturing activity outsourced in the developing economy, increases the bargaining power of its workers and, with it, its labor cost. The investigation underlines that an increasing labor-productivity remuneration in the developing economy may spark a reshoring process that depends on the agglomeration and endowment drivers characterizing an industry. The reshoring process can be narrowed by a flexible labor remuneration scheme, with wages indexed to the domestic concentration of manufacturing activity. The presence of sub-optimal location patterns points out the existence of a trade-off between stability and efficiency, which underlines that policy measures designed to make a country a more efficient location are neither sufficient nor necessary for preventing offshoring or ensuring reshoring.

An aging population in modern societies has put stress on public pension systems. To prevent social security deficits from increasing to unbounded levels of public debt we focus on two policies: reducing the generosity of pension benefits, determined by the government, and postponing the effective retirement age, chosen by employees. An atomistic employee would disregard the effect of his retirement decision on the public debt and would retire as soon as possible. Conversely, an ideal farsighted agency considering all current and future employees would postpone retirement, thereby alleviating the pressure on public debt and allowing a more generous long-run pension. The government may design a proper incentive strategy to induce myopic atomistic decision makers to act nonmyopically. This strategy is a two-part incentive with nonlinear dependence on the stock of public debt. It is credible if deceiving employees slightly adjust their retirement-age decisions to increments in the public debt.

This paper investigates the effects of R&D subsidies on aggregate product variety and endogenous productivity growth without scale effects. In a two-country model with imperfect knowledge diffusion, the larger country has a greater share of firms with higher productivity levels. The concentration of relatively productive firms increases knowledge flows between firms, causing an increase in firm-level employment in innovation. Accordingly, the aggregate growth rate is higher when counties are asymmetric than when they are similar in size. The larger scale of firm-level innovation activity reduces market entry, however, and aggregate product variety falls. In this framework, national R&D subsidies have positive effects on the industry share, relative productivity, and wage rate of the implementing country. If the smaller country introduces an R&D subsidy, aggregate product variety rises and productivity growth falls. If the larger country introduces an R&D subsidy, productivity growth rises, but aggregate product variety may rise or fall.

In this paper, we study the stationary and non-stationary equilibria of a deterministic, pure exchange, two-period overlapping generations model with habit persistence. We show that preferences with multiplicative habits can lead to quite different equilibrium outcomes compared to subtractive ones. The two most commonly adopted habit specifications can differ in terms of homotheticity, gross substitutability, and uniqueness of equilibria. We illustrate these differences in terms of steady-state equilibria, as well as local dynamics.

Bob Lucas is widely regarded as the most influential economist of the past 25–30 years, at least among those working in macro and monetary economics. His work provided the primary stimulus for a drastic overhaul and revitalization of that broad area, an overhaul that featured the ascendance of rational expectations, the emergence of a coherent equilibrium theory of cyclical fluctuations, and specification of the analytical ingredients necessary for the use of econometric models in policy design. These are the accomplishments for which he was awarded the 1995 Nobel Prize in Economic Sciences. In addition, he has made outstanding contributions on other topics—enough, arguably, for another prize. Among these are seminal writings on asset pricing, economic growth and development, exchange-rate determination, optimal fiscal and inflation policy, and tools for the analysis of dynamic recursive models.

Clearly, Bob Lucas is very much a University of Chicago product; he studied there both as an undergraduate and as a Ph.D. student and has been on the faculty since 1975. Also, he has served as chairman of the Chicago Department of Economics and two terms as an editor of the Journal of Political Economy. Nevertheless, I and several colleagues at Carnegie Mellon like to point out that Bob was a professor here in the Graduate School of Industrial Administration from 1963 until 1974, during which time he conducted and published the central portions of the work for which he was awarded the Nobel Prize. Consequently, I could not resist asking Bob a few questions about his GSIA years in the interview.

Many researchers in the economics profession have been impressed and inspired by Lucas's technical skills, but the clarity and elegance of his writing style also deserve mention, plus his choice of research topics. The latter is reflective of Bob's utter seriousness of purpose. Each of his projects attacks a problem that is simultaneously of genuine theoretical interest and also of considerable importance from the perspective of economic policy. There is nothing frivolous about Lucas's research, as he had occasion to remind me during our interview.

As is well known to those who have been around him, Bob Lucas is a person who never uses three words when one will suffice—but that one will usually be carefully chosen. This characteristic shows up in the interview below. As a departure from standard MD Interview practice, and with the Editor's permission, this interview was conducted at a distance—i.e., via mail and e-mail. It yielded a smaller number of pages than have previous interviews, but I think that readers will find them stimulating. The process of obtaining them was somewhat challenging but highly informative and thoroughly enjoyable for me.

This paper presents a Ramsey-like dynamic small open economy with endogenous labor migration. In the model, the domestic economy is free to borrow or lend as much as it wants at the given world interest rate, and individuals are supposed to be free to move from a country to another in response to the emergence of a wage differential between countries. Our analysis can be ideally split in two parts. Initially, we propose a baseline model in which only natives are allowed to save and invest in capital assets and traded bonds, whereas immigrants are credit constrained. Next, we provide an extension in which all individuals, including immigrants, have full access to international financial markets. We find that the steady state is always local indeterminate, and that the adjustment dynamics of the competitive equilibrium is dependent upon the initial level of the immigration ratio.

Franco Modigliani's contributions in economics and finance have transformed both fields. Although many other major contributions in those fields have come and gone, Modigliani's contributions seem to grow in importance with time. His famous 1944 article on liquidity preference has not only remained required reading for generations of Keynesian economists but has become part of the vocabulary of all economists. The implications of the life-cycle hypothesis of consumption and saving provided the primary motivation for the incorporation of finite lifetime models into macroeconomics and had a seminal role in the growth in macroeconomics of the overlapping generations approach to modeling of Allais, Samuelson, and Diamond. Modigliani and Miller's work on the cost of capital transformed corporate finance and deeply influenced subsequent research on investment, capital asset pricing, and recent research on derivatives. Modigliani received the Nobel Memorial Prize for Economics in 1985.

In macroeconomic policy, Modigliani has remained influential on two continents. In the United States, he played a central role in the creation of a the Federal Reserve System's large-scale quarterly macroeconometric model, and he frequently participated in the semiannual meetings of academic consultants to the Board of Governors of the Federal Reserve System in Washington, D.C. His visibility in European policy matters is most evident in Italy, where nearly everyone seems to know him as a celebrity, from his frequent appearances in the media. In the rest of Europe, his visibility has been enhanced by his publication, with a group of distinguished European and American economists, of “An Economists' Manifesto on Unemployment in the European Union,” which was signed by a number of famous economists and endorsed by several others.

This interview was conducted in two parts on different dates in two different locations, and later unified. The initial interview was conducted by Robert Solow at Modigliani's vacation home in Martha's Vineyard. Following the transcription of the tape from that interview, the rest of the interview was conducted by William Barnett in Modigliani's apartment on the top floor of a high-rise building overlooking the Charles River near Harvard University in Cambridge, Massachusetts. Those concluding parts of the interview in Cambridge continued for the two days of November 5–6, 1999 with breaks for lunch and for the excellent espresso coffee prepared by Modigliani in an elaborate machine that would be owned only by someone who takes fine coffee seriously.

Although the impact that Modigliani has had on the economics and finance professions is clear to all members of those professions, only his students can understand the inspiration that he has provided to them. However, that may have been adequately reflected by Robert Shiller at Yale University in correspondence regarding this interview, when he referred to Modigliani as: “my hero.”

This paper examines the financial stress interconnectedness among Greece, Ireland, Italy, Portugal, and Spain (GIIPS) economies and Germany. Based on market-level financial stress indices, we examine the stress transmission process as well as the causal network relationships in banking sector, bond, money, and stock markets. The period under investigation, 2001–2013, allows to test the effects of the 2007–2009 financial crisis as well as the subsequent European sovereign crisis. Using two alternative techniques for connectedness analysis, our evidence suggests that the peripheral economies of Italy and Spain play a highly significant role in the stress transmission in all markets, especially in the cases of banks and equity markets. Moreover, we visualize our results using network analysis. Contrary to common wisdom, Portugal, Ireland, and mainly Greece do not seem to have an important role in amplifying stress levels.

In response to the recession brought about by the COVID-19 pandemic, EU-wide macroeconomic policy has launched an unprecedented coordinated fiscal expansion across the EU (Next Generation EU or NGEU), financed by issuing common debt. Given NGEU’s nature, it is essential to take fiscal spillovers into consideration when assessing the overall macroeconomic effects of this fiscal expansion. We quantify the effects of the additional public investment for all Member States in a rich macro-model with a trade structure. Our model suggests that, on average, GDP effects are around one-third larger when explicitly accounting for the spillover effects from individual-country measures. For small open economies with smaller NGEU allocations, spillover effects account for the bulk of the GDP impact. We also quantify key transmission channels.

This paper investigates the potential sources of the mixed evidence found in the empirical literature studying asymmetries in the response of output to monetary policy shocks of different magnitudes. Further, it argues that such mixed evidence is a consequence of the exogenous imposition of the threshold that classifies monetary shocks as small or large. To address this issue, I propose an unobserved-components model of output, augmented by a monetary policy variable, which allows the threshold to be endogenously estimated. The results show strong statistical evidence that the effect of monetary policy on output varies disproportionately with the size of the monetary shock once the threshold is estimated. Meanwhile, the estimates of the model are consistent with a key implication of menu-cost models: smaller monetary shocks trigger a larger response on output.

We construct a microfounded model of money with Gul–Pesendorfer preferences. In each period, agents are tempted to spend all their money by the end of the period, and they suffer from the forgone utility that could have been obtained by adopting the tempting choice. We find that the Friedman rule may not be optimal. A positive nominal interest rate improves welfare because it reduces the real money balances and renders the temptation less attractive. The welfare gained by deviating from the rule is equivalent to 0.67% of consumption.

Coefficient drivers are observable variables that feed into time-varying coefficients (TVCs) and explain at least part of their movement. To implement the TVC approach, the drivers are split into two subsets, one of which is correlated with the bias-free coefficient that we want to estimate and the other with the misspecification in the model. This split, however, can appear to be arbitrary. We provide a way of splitting the drivers that takes account of any nonlinearity that may be present in the data, with the aim of removing the arbitrary element in driver selection. We also provide an example of the practical use of our method by applying it to modeling the effect of ratings on sovereign-bond spreads.

The dynamics of macroeconomic and financial series has evolved swiftly and asymmetrically since the end of the 1970s, and their statistical properties have also changed over time, suggesting complex relationships between economic and financial variables. The transformations can be explained by considerable changes in householder's behavior, market structures, and economic systems and by the alternation of exogenous shocks and financial crises that have affected the economic cycle, with significant evidence of time variation in the major economic variables. Hence, there is a need for new econometric protocols to take such changes into consideration. The introduction of ARMA (autoregressive moving average models) by Box and Jenkins (1970) led to the development of time-series econometrics, which had a major impact on the conceptual analysis of economic and financial data. This type of modeling offered a transition from a static setup to a new modeling process that reproduces the time-varying features of macroeconomic and financial series. However, the ARMA modeling system retains the constancy of the first and second moments, limits the phases of a cycle to symmetrical instances, and only reproduces the dynamics of stationary variables. It thus fails to adequately reproduce the nonstationary relationships between major economic and financial variables. Abrupt changes in economies and financial systems have given evidence of nonstationary series whose statistical properties are also time-varying, making it necessary to develop new econometric tools to capture the time variation of economic and financial series in the mean and in the variance, and to apprehend their dynamics in the short and long term. Among the most important and influential studies in the 1980s' econometrics literature were therefore those that dealt with the introduction of the ARCH (autoregressive conditional heteroskedasticity) model by Engle (1982) and the cointegration theory by Engle and Granger (1987). The ARCH model, which focuses on the time-varying features of volatility structure, was a major breakthrough, as it highlighted the importance of the second moment of time series, while the cointegration framework enabled the short- and long-term dynamics of nonstationary variables to be modeled.

Recent papers point to the problem that inflation-targeting models do not as of yet consider financial market stability that can considerably derail inflation-targeting monetary policy, implying significant nonzero crisis probabilities that could come along with large negative output and employment gaps. Credit flows and the instability of credit appear to be at the root of the financial instability problem. On the other hand, some authors recently questioned whether a too early and too strong leaning against the wind policy by central banks might have higher costs than benefits in terms of output and employment losses. In our paper, we include in an inflation targeting model a financial stabilization goal. In contrast to infinite horizon and two-period models, we propose a finite horizon model. The model is solved by using a new global solution algorithm, called Nonlinear Model Predictive Control (NMPC), exploring stabilizing/destabilizing effects of price and nonprice (credit volume) drivers of the output gap, inflation, and credit flows. We substantiate the theoretical part of the paper by approaching the subject empirically, relying to that end on a regime-switching structural vector autoregressive (VAR) for the euro area. The empirical model contains standard macroeconomic variables along with credit flows and loan interest rates, the central bank policy rate, and European Central Bank (ECB) balance sheet variables. The regime-switching feature of the model is meant to capture the state-dependent relationship between the variables, with specific nonlinearities having direct counterparts in the theoretical model. Based on a sign restriction methodology, we explore conventional and unconventional monetary policy shocks, loan supply, and demand shocks, under different regime assumptions to reveal the state-dependent effects of both interest rate and volume-based policies. The empirical results are used as guidance for the calibration of the theoretical model variants.

This paper analyzes the dynamics of an endogenous growth model with external habit formation and elastic labor supply. We first derive the conditions for the existence, uniqueness, and saddlepath stability of a feasible steady state with positive long-run growth. The global dynamics of the economy are characterized by phase-diagram analysis. Then we characterize the comparative static effects of shocks in preferences and production parameters analytically. The comparative dynamic effects of the shocks are characterized by phase-diagram analysis.

This paper explores single-equation nonlinear error correction (NEC) models with linear and nonlinear cointegrated variables. Within the class of semiparametric NEC models, we use smoothing splines. Within the class of parametric models, we discuss the interesting properties of cubic polynomial NEC models and we show how they can be used to identify unknown threshold points in asymmetric models and to check the stability properties of the long-run equilibrium. A new class of rational polynomial NEC models is also introduced. We found multiple long-run money demand equilibria. The stability observed in the money-demand parameter estimates during more than a century, 1878 to 2000, is remarkable.