The international migration literature has highlighted four key stylized facts from the perspective of the source country: (i) Migration rates are notably high, with some nations seeing over ten percent of their population living abroad. (ii) Certain developing countries have witnessed a significant exodus of skilled workers, commonly referred to as brain drain, spanning several decades. (iii) Migrants often maintain strong ties to their country of origin, evidenced by the substantial remittances they send back to their relatives. (iv) Migration is not necessarily permanent, as a considerable number of individuals return to their home country after a period spent abroad. In this paper, we present a theoretical model that endogenously explains these facts. Our model allows us to explore key issues in migration literature from a theoretical standpoint. We analyze the general equilibrium effects of migration, its long-term implications, and its welfare consequences. Additionally, we investigate whether the combined impact of return migration and remittances can counterbalance the effects of skilled migration. Finally, we evaluate the efficacy of policy interventions designed to mitigate the adverse effects of brain drain.

This paper explores the effect of fiscal policy on the welfare of heterogeneous agents with different income sources over the business cycle. Policy experiments allow the government to choose the cyclical properties of fiscal policy instruments conditional on long-run levels to separately maximize the welfare of entrepreneurs and workers. This policy choice creates welfare conflicts between the two groups, which is confirmed by empirical evidence. The government maximizes workers’ welfare by choosing procyclical capital income tax rates and countercyclical labor income tax rates while it optimizes entrepreneurs’ welfare with countercyclical capital income tax rates and strongly countercyclical labor income tax rates. The socially optimal policy is a tradeoff between the welfare of entrepreneurs and workers. The welfare conflict holds when the government modifies the cyclical behavior of policy in a crisis, or it adjusts the long-run level and cyclical behavior at the same time.

In a canonical model of heterogeneous agents with precautionary saving motives, Aiyagari [(1995) Journal of Political Economy 103(6), 1158–1175.] breaks the classical result of zero capital tax obtained in representative-agent models. Aiyagari argues that with capital overaccumulation the optimal long-run capital tax should be strictly positive in order to achieve aggregate allocative efficiency suggested by the modified golden rule (MGR). In this paper, we find that, depending on the sources of capital overaccumulation, capital taxation may not be the most efficient means to restore the MGR when government debt is feasible. To demonstrate our point, we study optimal policy mix in achieving the socially optimal (MGR) level of aggregate capital stock in an infinite horizon heterogeneous-agents incomplete-markets economy where capital may be overaccumulated for two distinct reasons: (i) precautionary savings and (ii) production externalities. By solving the Ramsey problem analytically along the entire transitional path, we reveal that public debt and capital taxation play very distinct roles in dealing with the overaccumulation problem. The Ramsey planner opts neither to use a capital tax to correct the overaccumulation problem if it is caused solely by precautionary saving—regardless of the feasibility of public debt—nor to use debt (financed by consumption tax) to correct the overaccumulation problem if it is caused solely by production externality (such as pollution)—regardless of the feasibility of a capital tax. The key is that the MGR has two margins: an intratemporal margin pertaining to the marginal product of capital (MPK) and an intertemporal margin pertaining to the time discount rate. To achieve the MGR, the Ramsey planner needs to equate not only the private MPK with the social MPK but also the interest rate with the time discount rate—neither of which is equalized in a competitive equilibrium. Yet public debt and a capital tax are each effective only in calibrating one of the two margins, respectively, but not both.

This paper studies the implications of price flexibility on output volatility under menu costs and finds price flexibility to be output-destabilizing under supply shocks, but not necessarily so under demand shocks. We illustrate that such a result hinges on the extent to which firms can adjust along both the intensive and the extensive margins, the latter of which is often absent in the literature.

Soon after the start of transition to a market economy in the early 1990s, Poland has experienced both a dramatic decline in the fertility rate and an increase in the share of students among young high-school graduates. These two processes significantly changed the age structure of population and average income characteristics of households. Using a general equilibrium model with heterogeneous households and uninsured income shocks, I try to assess the impact of these changes on the Polish economy as a whole and inequalities within it. I find that, in the long term, the positive effects of the educational change on output per capita will more than offset the negative impact of lower fertility. I also show that the educational change increases income and consumption inequalities, while the fertility change decreases inequality in assets.

We investigate the aggregate and distributional effects of banking spreads in an economy with informality. We build a heterogeneous agents model with incomplete markets, credit frictions, and a rich occupational choice setting, in which informality is an option for both employers and workers. The main finding is that reductions in spreads for formal firms increase wages, output, and welfare but have a deleterious impact on unemployment and inequality. Dropping spreads for informal firms lead to reduction in inequality indicators at the expense of consumption and welfare. By calibrating the model for Brazil, we also find that a hypothetical extinction of the informal sector can be harmful for poor agents, but combined with a spread reduction, it can generate strong positive effects on output and welfare.

This paper examines the consequences of international financial integration in a two-sector standard incomplete markets model with occupational choice under risk and financial constraints affecting entrepreneurial activity. We endogenize international productivity differences and discuss the implications of international integration for the macroeconomy, inequality, and welfare. Lending countries are characterized by tighter domestic constraints and experience an increase in gross national product, whereas the gross domestic product effect is ambiguous. We conclude that international integration is beneficial only for economies where there are substantial financial constraints on entrepreneurial activity. Otherwise, a majority of households suffer, due to the unequal distribution of welfare gains and losses across the heterogeneous population.

Can increasing market power cause a decrease in the aggregate savings? We answer this question by using a heterogeneous agents model that features both idiosyncratic labor and capital income risk. Under complete markets, the saving rate does not depend on the degree of market power, but when markets are incomplete, higher markups substantially reduce the aggregate saving rate. This is due to endogenous changes in the distribution of income and wealth. A calibration of the model using the observed changes in market power in the United States since the 1970s closely matches the decline in the US saving rate. Furthermore, when market power increases, the model generates distributional changes that are consistent with the data.

We add households with heterogeneous discount factors and constrained credit to a research and development (R&D)-based endogenous growth model. Borrowers' access to credit has profound implications for growth. The direction and magnitude of this effect depend on preferences over labor supply. If labor supply is highly elastic and households do not smooth their labor supply between labor that produces output and R&D, annual growth decreases from 11.6% to approximately zero as the debt-to-capital ratio rises from 0 to 1.38. If households instead have a strong preference for smoothing their labor supply, then growth increases from 2.91% to 3.83% as the debt-to-capital ratio rises from 0 to 1.55. In both cases, less elastic labor supply weakens these effects. The results are similar if existing ideas do not affect the creation of new ideas. Now, when households do not smooth their labor supply, less debt results in faster growth, and productivity and output converge to much higher values.

A general equilibrium model with financial frictions in which individuals may encounter unobservable investment opportunities is developed along the lines of Kiyotaki and Moore (2012). I study efficiency properties induced by money and monetary policy when financial frictions prevent optimal equilibrium allocations. By providing closed-form solutions to all prices, allocations, welfare, and, especially, the distribution of individuals with respect to assets, I show that the Friedman rule achieves maximal social welfare, independent of how tight the financial constraints may be. The same level of welfare would be induced by an omniscient central planner able to verify who has an investment opportunity.

We introduce public spending, financed through income taxation, into the Ramsey model with heterogeneous agents. Public spending as a source of welfare generates more complex dynamics. In contrast to previous contributions focusing on similar models but with wasteful public spending, limit cycles through Hopf bifurcation and expectation-driven fluctuations appear if the degree of capital–labor substitution is high enough to be compatible with capital income monotonicity. Moreover, unlike frameworks with a representative agent, our results do not require externalities in production and are compatible with a weakly elastic labor supply with respect to wage.

Models of endogenous growth have not been able to account for the variety of empirically observed distributional properties of the returns to innovation, in part, because of the limitations necessarily imposed on competition to cope with increasing returns to scale. Exponential growth, fat tails, Pareto–Levy distributed upper tails, and upper value outliers, are associated with increasing returns to scale and innovation. At the same time, properties such as bifurcated research investment strategies, bimodal returns to innovation, and Laplace distributed firm growth rates are products of competition. We build an agent-based model of endogenous technical change in which heterogeneous investments in patented knowledge and increasing returns to scale emerge these distributional properties within a competitive market. The combination of heterogeneous agents, costly information, and patents allow for a competitive landscape to persist amidst increasing returns. The ability of model to foster a coexistence of competition and increasing returns underlies the observed distributional properties.

Since the company declared bankruptcy in June 2009, shares of General Motors stock (now known as Motors Liquidation Company) have continued to trade at a high volume while maintaining a market capitalization near $300 million through most of 2010. Anecdotal evidence strongly suggests that both rational speculators and uninformed investors (often mistaking Motors Liquidation for the new, reorganized GM) have purchased the stock. We develop a theoretical asset-pricing model that includes both types of agents. We present two major results. First, the most frequent state is one where a small fraction of rational agents ensure that the share price behaves as if all agents are rational. A second state exists where all rational agents exit and the share price is inflated. Second, fitting the model to Motors Liquidation, we find evidence of irrational asset pricing for this firm. We find little evidence of similar behavior in the share prices of the thirty stocks that compose the Dow Jones Industrial Average.

Inspired by the theoretically oriented dynamic analysis of moving average rules in the model of Chiarella, He, and Hommes (CHH) [Journal of Economic Dynamics and Control 30 (2006), 1729—1753], this paper conducts a dynamic analysis of a more realistic microstructure model of continuous double auctions in which the probability of heterogeneous agents trading is determined by the rules of either fundamentalists mean-reverting to the fundamental or chartists choosing moving average rules based on their relative performance. With such a realistic market microstructure, the model is able not only to obtain the results of the CHH model but also to characterize most of the stylized facts including volatility clustering, insignificant autocorrelations (ACs) of returns, and significant slowly decaying ACs of the absolute returns. The results seem to suggest that a comprehensive explanation of several statistical properties of returns is possible in a framework where both behavioral traits and realistic microstructure have a role.

I develop an algorithm for solving dynamic models in which individual decision rules and the cross-sectional distribution of agents' characteristics influence each other. To illustrate the algorithm, I solve an endowment economy with incomplete markets, a continuum of heterogeneous agents, and aggregate shocks. The key innovation of the algorithm is to parameterize the (cross-sectional) density with a flexible functional form, which makes it possible to avoid simulation techniques. The paper shows how to check for accuracy and establishes links between the properties of the incomplete-markets economy and the aspects involved in obtaining a numerical solution.

We explore alternative approaches to numerical solutions of large rational-expectations models. We discuss and compare several current alternatives, focusing on the trade-offs in accuracy, space, and speed. The models range from representative-agent models with many goods and capital stocks, to models of heterogeneous agents with complete or incomplete asset markets. The methods include perturbation and projection methods. We show that these methods are capable of analyzing moderately large models even when we use only elementary, general-purpose numerical methods.

This paper studies the role played by differences in risk aversion in affecting the long-run distribution of wealth across agents in the context of an endowment economy. The economy is populated by two types of Epstein-Zin agents who differ only in their attitudes toward risk. By choosing riskier portfolio strategies, less-risk-averse agents enjoy returns on their investments characterized by a higher mean and a higher variance than the ones enjoyed by more-risk-averse agents. The former effect tends to make less-risk-averse agents wealthier over time, whereas the latter tends to make them poorer. The paper shows that, contrary to the results obtained using standard expected utility preferences, for some parameter values the long-run distribution of wealth is dominated by more-risk-averse agents.

This paper explores multiasset market dynamics. We consider a limited number of markets on which two types of agents are active. Fundamentalists specialize in a certain market to gather expertise. Chartists may switch between markets since they use simple extrapolative methods. Specifically, chartists prefer markets that display price trends but that are not too misaligned. The interaction between the traders causes complex dynamics. Even in the absence of random shocks, our artificial markets mimic the behavior of actual asset markets closely. Our model also offers reasons for the high degree of comovements in stock prices observed empirically.

In recent decades, the structure of wages in the U.S. economy has shifted to favor workers with college degrees over those without college degrees. Concurrently, there has been an increase in the share of the workforce that is college educated. We build an overlapping generations model in which skill-biased technological change drives both rising wage inequality and a rising percentage of skilled (educated) workers in the labor force. We explore the implications for agent welfare and for the distribution of income of different factor taxation choices. We find that higher tax rates on capital and lower tax rates on unskilled labor can yield steady-state welfare gains across a heterogeneous population, and that these gains increase as the economy experiences technological change that favors skilled labor. Moreover, these shifts in taxation can lower net wage inequality. Steady-state welfare gains, however, come at the expense of agents alive upon implementation.