My dissertation studies the effect of macroeconomic policies both theoretically and empirically. In Chapter 1, I empirically estimate a DSGE model with search and matching frictions, endogenous job separation, and real wage rigidities to examine the main driving forces behind unemployment fluctuations. I find that shocks to unemployment benefits have historically been important for unemployment fluctuations, and the extension of unemployment benefits during the recent recession contributed to the higher unemployment rate. In Chapter 2, I study the impact of liquidity shocks on the economy, the effectiveness of alternative government policies, and the role played by the zero lower bound on the nominal interest rate. I find that extended unem...