My dissertation investigates two models of macroeconomics with heterogeneous agents. The first chapter analyzes a setup where agents are ex ante identical, yet receive idiosyncratic income shocks which make them heterogeneous ex post. A private information friction gives rise to incomplete risk-sharing as a constrained-efficient allocation. The second chapter again considers ex post heterogeneous agents: they have identical preferences but face idiosyncratic shocks to their earning capacity. There the focus is not on risk-sharing, but on the aggregate consequences for labor supply.

"Chapter 1 develops a heterogeneous-agent general equilibrium model that incorporates both intensive and extensive margins of labor supply. A nonconvexity in the mapping between time devoted to work and labor services distinguishes between extensive and intensive margins. We consider calibrated versions of this model that differ in the value of a key preference parameter for labor supply and the extent of heterogeneity. The model is able to capture the key features of the empirical hours worked distribution, including how individuals transit within this distribution. We then study how the various specifications influence labor supply responses to temporary shocks and permanent tax changes, with a particular focus on the intensive and extensive margin elasticities in response to these changes. We find important interactions between heterogeneity and the extent of curvature in preferences. Chapter 2 builds a model of family labor supply in which individuals choose between full-time work, part-time work, and nonemployment. The model is calibrated to replicate the movements of both male and female workers among these states. The willingness to substitute hours over time (the so-called intertemporal elasticity of labor supply) is critical for many economic analysis. A common strategy for uncovering the value of this willingness is to carry out structural estimation on micro panel data. One general issue in this estimation exercises using micro data is that misspecification of the constraints that individuals face is likely to influence inference about preference parameters. In the model economy, although the individual labor supply problem is a discrete choice problem, individuals are able to adjust hours along the intensive margin by moving between part-time and fulltime work. Intuitively, adjustment along the intensive margin potentially allows one to estimate the true value of the underlying curvature parameter describing the utility from leisure. We explore the extent to which standard labor supply methods can achieve this in our setting. Although these methods deliver precise estimates that are significantly different from zero, the estimates are effectively unrelated to the true underlying values. These methods also deliver elasticity estimates for women, even when the underlying preference parameters are the same for men and women. Chapter 3 investigates the optimal progressive tax code in an incomplete-market economy in which households are linked intergenerationally by altruism and earning ability. The model economy is calibrated to that of the US with the progressive tax code suggested by Gouviea and Strauss (1994). First, I compute the equilibrium with the optimal progressive tax code. Second, I investigate the extent to which the size of government welfare programs affects the optimal progressivity of the income tax code. I find that the optimal tax code for an economy populated with altruistic households is approximately equivalent to a proportional tax of 23.1% with a fixed deduction of approximately $17,000 in 1990 US dollars. For an economy populated with non-altruistic households, however, these numbers are 18.8% and $12,000 respectively. This result implies that inequality is more severe in an economy with intergenerational links so that the policy maker requires a more progressive tax system to provide insurance. Additionally, I find that when the size of the government welfare program is chosen carefully, the additional insurance benefits from the progressive income tax code disappear"--Pages iv-v.

"This dissertation consists of essays addressing the macroeconomic outcomes of heterogeneous agent general equilibrium models with micro-level frictions. Each chapter employs both empirical and quantitative macroeconomic methods. The first chapter studies the impact of elevated volatility on the effectiveness of monetary policy on aggregate investment under firm-level capital adjustment costs. I argue that monetary policy is less effective at stimulating investment during periods of elevated volatility in firm-level TFP than during normal times. Empirically, I document that high volatility weakens investment responses to monetary stimulus. I then develop a heterogeneous firm New Keynesian model with lumpy investment to interpret these findings. In the model, non-convex capital adjustment costs create a sizable extensive margin of investment which is more sensitive to changes in both interest rate and volatility than the intensive margin. When volatility is high, firms tend to stay inactive at the extensive margin, so monetary stimulus motivates less investment at the extensive margin. I find that the quantitative implications of the model are primarily shaped by the specifications of the capital adjustment costs. Unlike much of the prior literature, I use the dynamic moments of investment to identify this key model element. Based on this parameterization, high volatility reduces the effectiveness of monetary stimulus for investment by 30%. This reduction is about half of what I find in the data. Therefore, the effect of monetary policy depends on both the lumpy nature of firm-level investment and fluctuations in volatility. The second chapter studies the role of migration and housing constraints in determining income inequality within and across Chinese cities. Combining microdata and a spatial equilibrium model, we quantify the impact of the massive spatial reallocation of workers and the rapid growth of housing costs on the national income distribution. We first show several stylized facts detailing the strong positive correlation between migration inflows, housing costs, and imputed income inequality among Chinese cities. We then build a spatial equilibrium model featuring workers with heterogeneous skills, housing constraints, and heterogeneous returns from housing ownership to explain these facts. Our quantitative results indicate that the reductions in migration costs and the disproportionate growth in productivity across cities and skills result in the observed massive migration flows. Combining with the tight land supply policy in big cities, the expansion of the housing demand causes the rapid growth of housing costs, and enlarges the inequality between local housing owners and migrants. The counterfactual analysis shows that if we redistribute land supply increment by migrant flow and increase land supply toward cities with more migrants, we could lower the within-city income inequality by 14% and the national income inequality by 18%. Meanwhile, we can simultaneously encourage more migration into higher productivity cities"--Pages vii-viii.

"This thesis extends the macroeconomic theory with heterogeneous agents by taking account of heterogeneous households' interaction among themselves, in the form of comparing their consumptions or incomes, and by allowing heterogeneous firms to interact in a strategic fashion. In Chapter 2, I study how behavioral hypotheses such as the concern for status (relative consumption) and inequality aversion can lead to useful predictions about the evolution of wealth distribution and asset accumulation. Households are heterogeneous in terms of initial endowments and idiosyncratic shocks to their labor productivity. I propose a generalized concept of consumption externalities which include as special cases the concern for relative consumption, and preferences that display inequality aversion. In Chapter 3, I focus on interactions among heterogeneous firms in an oligopolistic framework. I assume that that the products offered by these firms are not perfect substitutes. More important, the degree of substitutability may vary across products within the industry. I offer a general formulation of industry structure such that monopoly, oligopoly, and monopolistic competition can be obtained as special cases. In Chapter 4, we study how preferences that display ambiguity aversion play a role in the job search process and affects the equilibrium rates of unemployment and vacancy. Ambiguity refers to the lack of information about probability distributions. The traditional job search model assumes that there are random matches between job seekers and firms (or vacancies), and the random draws have objective probability distributions that are known to both sides of the markets. We modify this model and assume that economic agents are uncertain about the underlying probability distributions. This chapter contributes to our understanding of how ambiguity aversion affects the unemployment rate and aggregate productivity." --

"This thesis is a collection of essays on development economics from a macro-quantitative perspective. These issues are studied in subsequent chapters. In Chapter 1, I study migration from a quantitative perspective. Developing countries have experienced an outstanding outflow of skilled workers (brain drain) over the last several decades. Additionally, migrants tend to be tied to their country of birth, since they send large amounts of remittances to their relatives. Furthermore, migration is not permanent, since a considerable number of workers return to their country of birth after a migration spell. In this paper I develop a model that is consistent with these facts. I use this model to address some important issues in the migration literature from a theoretical perspective. I study the general equilibrium effects of migration, its long-term effects, its welfare effects, and evaluate whether the joint effect of return migration and remittances is strong enough to offset the effects of the brain drain (effects of skilled migration). In a final step, I evaluate the effectiveness of policy interventions that attempt to offset the effects of the brain drain. In Chapter 2, I study the economic effects of an anti-poverty conditional cash transfers (CCT) policy by using a stylized dynamic general equilibrium model. I look at the program's impact on output, human capital, poverty and income inequality. I also study its welfare implications and its effects on the intergenerational transmission of poverty. The quantitative analysis reveals that a long-term implementation of this anti-poverty program helps to reduce the intergenerationa transmission of poverty. In aggregate terms the welfare gain is small but varies across agents; the winners are those who are in the lower tail of the income distribution and the losers are those located in the upper tail. Finally, this program increases the human capital of households and, through this channel, induces a consistent reduction of both poverty and income inequality"--Page v-vi.

This dissertation investigates several business cycle relationships when economic agents are heterogeneous. The particular focus is on the interactions between the cross-section of agents and the aggregate state of the economy. The first chapter shows that, when occasionally binding capacity constraints limit the production of heterogeneous firms, demand shocks can endogenously generate a number of important business cycle regularities: recessions are deeper than booms are high, firm-level volatility is countercyclical, the aggregate Solow residual is procyclical and the fiscal multiplier is countercyclical. A baseline calibration of a basic New Keynesian DSGE model with capacity constraints shows that this mechanism can explain more than a quarter of the empirically observed asymmetry in output, and matches the cyclicality of firm-level profitability dispersion and of the measured Solow residual. The model implies fluctuations in the fiscal multiplier of around 0.12 between expansions and recessions. Chapter two takes a different approach to firm level uncertainty, exploring how recessions can cause an endogenous rise in firm risk. If heterogeneous firms face real and financial frictions, then a shock to the mean of aggregate productivity endogenously leads to countercyclical profitability risk through firms' heterogeneous responses in price setting. Additionally, the mechanism endogenously generates countercyclical credit spreads and credit spread dispersion. The model explains a large share of the observed fluctuations in profitability dispersion (69%) and in credit spreads (40%) through fluctuations in aggregate TFP holding productivity risk constant. This suggests that the scope for uncertainty shocks to explain recessions may be smaller than previously thought. The third chapter focuses on distributional effects of oil price shocks on the household side. In the model, household behavior replicates two patterns found in household-level data which show that gas consumption increases with income, but on the intensive margin gasoline consumption as a share of the household's budget decreases with income. The model includes gas consumption in household utility on top of a fixed minimum level of gas consumption. Calibrated simulations suggest that a shock to the gas price is almost twice as costly for relatively poor households than for relatively rich households.