YU, ZHIXIU2022-09-132022-09-132022-06https://hdl.handle.net/11299/241633University of Minnesota Ph.D. dissertation. 2022. Major: Economics. Advisor: Mariacristina De Nardi. 1 computer file (PDF); 163 pages.This dissertation consists of three chapters studying three important macroeconomic questions. The first chapter studies conditions under which cryptocurrency is valued and under which it coexists with fiat money, using search-theoretic models. A cryptocurrency economy is one in which private agents’ decisions determine the stock of money and in which the marginal cost of producing money is increasing in the existing nominal stock. I show that the inflation rate must be zero in a stationary monetary equilibrium. This result is in sharp contrast to models with fiat money in which the stock of money is exogenously given. In fiat money economies, the inflation rate is determined by the rate of growth of the money stock. My result is also in sharp contrast with other types of private money economies, in which the inflation rate must necessarily be different from zero. In such private money economies, the cost of producing additional money does not depend on the existing nominal stock. Moreover, I show that cryptocurrency and fiat money can circulate at the same time and that the rates of return on these two assets may not be the same. Competition with cryptocurrency restricts the government’s ability to over-issue fiat money and thereby might improve on pure fiat money equilibria without government commitment. The second chapter documents the labor supply trends of older men in the United States and changes in Social Security rules that might be the important factors leading to the rise in the labor supply. The labor supply of men over age 60 has been rising over the past several decades, along both extensive and intensive margins. This trend in older men’s labor is particularly remarkable given that other age groups, such as younger men aged 21-55, exhibited a significant decline in work hours during the same period. In this chapter, I focus on two cohorts of American men: those born in the 1930s and 1950s. I show that the 1950s cohort, relative to the 1930s cohort, supplied more labor from age 60 to age 69, in terms of both labor participation rates and hours worked by workers. For instance, on average, participation rates at ages 60-69 for the 1950s cohort are 9.6 percentage points higher than those for the 1930s cohort, and hours worked by workers increased by 11.5% for the same age group between the two cohorts. Moreover, comparing labor supply behaviors by health status across cohorts over the life cycle, I find a new fact that these increases in participation rates and hours per worker across cohorts are mainly driven by people who were in good health. Further, the labor supply behaviors across cohorts are not significantly different by educational and occupational groups. In addition, compared to the older cohort, the younger cohort faced different Social Security rules: the NRA was postponed from age 65 to age 66; the RET was eliminated for individuals at the NRA or older; and the DRC was raised from around 4.5% to 8%. The third chapter uses a rich structural model to evaluate the impact of Social Security rules on the work decisions for American households. The labor supply of older men increased from the 1930s to the 1950s cohort. This chapter explores the role of three Social Security changes in determining these differences: a delayed normal retirement age, increased delayed retirement credits, and a change in the earnings test that was eliminated beyond the retirement age, and evaluates the effects of several proposed reforms to the Social Security program on individuals’ behaviors. I develop and estimate a rich dynamic life-cycle model of labor supply, savings, and Social Security application for healthy and unhealthy people using the Method of Simulated Moments for the 1930s birth cohort. The model captures the key structure of the Social Security retirement benefits, pension systems, and disability insurance, while taking into account uncertainties in health and disability, survival rates, wages, and medical expenditures. My model matches well the observed life-cycle profiles of employment, hours worked by workers, and savings for healthy and unhealthy people from the Panel Study of Income Dynamics data, and generates labor supply elasticities that rise with age and are smaller for healthy workers. It shows that the joint effects of the three changes in Social Security rules account for over 73% of the observed rises in labor force participation and hours per worker by the 1950s cohort. Of the three changed rules, the change in the earnings test contributes the most to the labor dynamics of older men. Additional policy experiments suggest that postponing the retirement age has little effect on older workers, while eliminating the earnings test and reducing retirement benefits by 23% would further increase older-age participation by 3.4 and 5.1 percent, respectively.enCryptocurrencyCurrency CompetitionLife CycleOlder WorkersSocial SecurityThesis or Dissertation