My dissertation consists of three chapters studying the heterogeneity in the labor market. Chapter 1 studies the by-age employment heterogeneity in response to technology shocks. Chapter 2 studies the by-age labor force participation heterogeneity in response to macroeconomic shocks. Chapter 3 studies the effect of monetary policy on the employment of occupations with different levels of routine task intensity. A central question in macroeconomics is how employment changes in response to technological progress. In Chapter 1, I broaden this question by investigating if there exist age-specific effects. I use the mixed autoregression (MAR) model to explicitly model the employment to population ratio as a function of age. The results show the responses of young and old employment ratios are much more negative than prime-age, and the response of the young is three times lower than that of the old. Moreover, the forecast error variance decomposition results show that technology shocks' contribution decreases by age. The labor force participation rate is weakly procyclical, as opposed to employment, which is strongly procyclical. Therefore, labor force participation is mostly assumed to be constant in the literature. However, the young, prime-age, and old participation rates are heterogeneous in cyclicality and volatility. In Chapter 2, I study the heterogeneity in the participation of 16-65 old in response to important macroeconomic shocks. I extend the identification scheme in the MAR model from zero to sign restrictions, which enable me to include labor market shocks important for explaining participation rate fluctuations. The results show that young, prime-age, and old participation rates respond differently to the technology, demand, labor supply, and wage bargaining shocks.Routine occupation employment share has decreased, while non-routine occupation employment share has increased since the 1980s. This trend of job polarization has been contributing to the growth in wage inequality in the US. In Chapter 3, I study the effect of a contractionary monetary policy shock on occupational employment with different levels of routine task inputs in a MAR model. I show that routine occupation groups' employment, especially those with higher offshorability, are disproportionally affected by a contractionary monetary policy shock.

In my thesis, I study the effects of agents' heterogeneity on labor market outcomes, with particular focus on sorting, performance, wages, and inequality. Chapter one studies multidimensional matching between workers and jobs. Workers differ in manual and cognitive skills and sort into jobs that demand different combinations of these two skills. To study this multidimensional sorting, I develop a theoretical framework that generalizes the unidimensional notion of assortative matching. I derive the equilibrium in closed form and use this explicit solution to study biased technological change. The key finding is that an increase in worker-job complementarities in cognitive relative to manual inputs leads to more pronounced sorting and wage inequality across cognitive relative to manual skills. This can trigger wage polarization and boost aggregate wage dispersion. I then estimate the model for the US during the 1990s. I identify a significant increase in complementarities of cognitive inputs and in cognitive skill-bias in production. Counterfactual exercises suggest that these technology shifts can account for observed changes in worker-job sorting, wage polarization and a significant part of the increase in US wage dispersion. Chapter two develops a theory that links differences in men's and women's social networks to disparities in their labor market performance. We are motivated by our empirical finding that men's and women's networks differ. Men have a higher degree (more network links) than women, but women have a higher clustering coefficient (a woman's friends are also friends among each other). In our model, a worker with a higher degree has better access to information. In turn, a worker with a higher clustering coefficient faces more peer pressure. Both peer pressure and access to information can attenuate a team moral hazard problem in the work place. But whether peer pressure or access to information is more important depends on the work environment. We find that, in environments where uncertainty is high, information is crucial and, therefore, men outperform women / in line with findings from sectors with high earnings' uncertainty like the financial or film industry.

My dissertation focuses on the heterogeneity in labor markets. The first chapter proposes an explanation for the unemployment rate difference between skill groups. Low skill workers (workers without a four year college degree) have a higher unemployment rate. The reason for that " ... is mainly because they (low skill workers) are more likely to become unemployed, not because they remain unemployed longer, once unemployed" (Layard, Nickell, Jackman, 1991, p. 44). This chapter proposes an explanation for the difference in job separation probabilities between these skill groups: high skill workers have lower job separation probabilities as they are selected more effectively during the hiring process. I use a labor search model with match specific quality to quantify the explanatory power of this hypothesis on differences in job separation probabilities and unemployment rates across skill groups. The second chapter analyzes the effects of one channel of interaction (job competition) between skill groups on their labor market outcomes. Do skilled workers prefer unskilled jobs to being unemployed? If so, skilled workers compete with unskilled workers for those jobs. Job competition generates interaction between the labor market outcomes of these groups. I use a heterogeneous agents model with skilled and unskilled workers in which the only interaction across groups is the job competition. Direct effects of job competition are reducing skilled unemployment rate (since they have a bigger market) and increasing the unskilled unemployment rate (since they face greater competition). However number of vacancies respond to job competition in equilibrium. For instance, unskilled firms have incentives to open more vacancies since filling a vacancy is easier if there is job competition. Thus how unskilled unemployment and wages are affected by job competition depends on which effect dominates. The results for reasonable parameter values show that job competition does reduce the average unemployment rate. It reduces the skilled unemployment rate more, generating an increase in unemployment rate inequality. However, the employment rate at skilled jobs is unaffected. The third chapter focuses on skill biased technological change. Skill biased technological change is one of the explanations for the asymmetry between labor market outcomes of skill groups over the last few decades. However, during this time period there were also skill neutral shocks that could contribute to these outcomes. The third chapter analyzes the effects of skill biased and neutral shocks on overall labor market variables. I use a model in which skilled and unskilled outputs are intermediate goods, and final good sector receives all the shocks. A numerical exercise shows that both skilled and unskilled unemployment rates respond to shocks in the same direction. The response of unemployment rate to skill neutral shocks is bigger than the response to skill biased shocks for both skill groups. However, the unskilled unemployment changes more than the skilled unemployment rate as a response to skill neutral shocks. Thus, skill neutral shocks reduce the unemployment rate gap between skill groups.

It is often argued that the labor market outcomes of several ?problem groups? of German workers suffer disproportionately in an economic downturn. These groups are women, the unskilled, and young and old workers, respectively. Using monthly individual-level data for West Germany for the period 1983 to 1994, this paper explores both the demographic heterogeneity of German unemployment in the long term, and the cyclical sensitivity of the unemployment experience across demographic groups. The analysis moves beyond that of unemployment rates to a detailed investigation of transition rates from employment to unemployment and vice versa. While long-term differences across demographic groups are dominating the structure of both job loss and re-employment, estimation of a nonlinear regression model reveals additional aspects of cyclical sensitivity. In particular, young workers experience drastically more pronounced swings in their labor market performance than the average worker, whereas old workers seem basically isolated from the economic cycle. By contrast, in terms of its cyclical sensitivity, the labor market performance of women and of unskilled workers is not dramatically different from that of the average worker.

This dissertation contains several lines of research in macroeconomics and labor economics conducted during the course of my phd. The unifying theme of this research is the study of labor markets that are subject to macro-search frictions and are populated by heterogeneous workers. Combining these features is important for our understanding of the functioning of labor markets, both from a positive and normative standpoint. The first chapter of this dissertation is resolutely on the positive side. It analyzes how the combination of labor market frictions and worker heterogeneity in skills can shed light on the observed fluctuations in entries into and exits out of the labor force. The second chapter is also on the positive ground, but it brings labor market policies to the fore of the analysis. Along with heterogeneity in human capital over the lifecycle, it shows how some policy tools have contributed to the divergent employment experiences of older workers in Europe and in the United States since the 1980s. The third chapter more naturally lends itself to policy implications. It provides a quantitative study of the employment and welfare effects of statutory severance payments in an economy with wealth heterogeneity reflecting the absence of perfect insurance markets faced by risk-averse workers.