This dissertation studies the Federal Reserve\u27s unconventional monetary policy tools: the large-scale asset purchases (LSAPs) and the extended period of a near-zero interest rate policy (ZIRP). In the first chapter, we simulate the Federal Reserve second LSAPs program in a dynamic stochastic general equilibrium (DSGE) model with bond market segmentation estimated on U.S. data. GDP growth increases by less than a third of a percentage point and inflation barely changes relative to the absence of intervention. The key reasons behind our findings are small estimates for both the elasticity of the risk premium to the quantity of long-term debt and the degree of financial market segmentation. Absent the commitment to keep the nominal interest...