Book excerpt: The essays in my dissertation examine how economic downturn and job composition affect heterogeneous workers in the labor market. In Chapter 1, I assert that slow recovery in aggregate employment compared to aggregate output in the United States consist of jobless growth in manufacturing and information industries. I observe the industrial transition of unemployed workers to demonstrate labor reallocation triggered by a decline of middle-wage jobs. I simulate the jobless growth and vertical reallocation in general equilibrium model with sorting and optimal submarket choices. In Chapter 2, I quantify recession effect on annual labor income for heterogeneous workers. I find that low-wage workers earn less annually mostly because of lower working hours through unemployment, whereas high-wage workers lose their annual earnings primarily due to lower hourly rates of job-to-job transition. I explain decreasing layoff risk (extensive margin) and increasing wage-cut risk (intensive margin) to previous wage rate in an on-the-job search model with real business cycles. In Chapter 3, I reassess transitional dynamics of unemployment and vacancy rate in a homogeneous agents search model, by allowing sunk entry costs and discrete productivity process. The entry costs allow a positive outside option for a vacant firm so that an outside firm and vacant firm make different labor market participation and hiring choices. When economy transit between two steady-state equilibria, the vacancy rate is no more a jump variable, and an outward (inward) shift is expected before reaching a low (high) productivity equilibrium.