"Chapter 1 develops a heterogeneous-agent general equilibrium model that incorporates both intensive and extensive margins of labor supply. A nonconvexity in the mapping between time devoted to work and labor services distinguishes between extensive and intensive margins. We consider calibrated versions of this model that differ in the value of a key preference parameter for labor supply and the extent of heterogeneity. The model is able to capture the key features of the empirical hours worked distribution, including how individuals transit within this distribution. We then study how the various specifications influence labor supply responses to temporary shocks and permanent tax changes, with a particular focus on the intensive and extensive margin elasticities in response to these changes. We find important interactions between heterogeneity and the extent of curvature in preferences. Chapter 2 builds a model of family labor supply in which individuals choose between full-time work, part-time work, and nonemployment. The model is calibrated to replicate the movements of both male and female workers among these states. The willingness to substitute hours over time (the so-called intertemporal elasticity of labor supply) is critical for many economic analysis. A common strategy for uncovering the value of this willingness is to carry out structural estimation on micro panel data. One general issue in this estimation exercises using micro data is that misspecification of the constraints that individuals face is likely to influence inference about preference parameters. In the model economy, although the individual labor supply problem is a discrete choice problem, individuals are able to adjust hours along the intensive margin by moving between part-time and fulltime work. Intuitively, adjustment along the intensive margin potentially allows one to estimate the true value of the underlying curvature parameter describing the utility from leisure. We explore the extent to which standard labor supply methods can achieve this in our setting. Although these methods deliver precise estimates that are significantly different from zero, the estimates are effectively unrelated to the true underlying values. These methods also deliver elasticity estimates for women, even when the underlying preference parameters are the same for men and women. Chapter 3 investigates the optimal progressive tax code in an incomplete-market economy in which households are linked intergenerationally by altruism and earning ability. The model economy is calibrated to that of the US with the progressive tax code suggested by Gouviea and Strauss (1994). First, I compute the equilibrium with the optimal progressive tax code. Second, I investigate the extent to which the size of government welfare programs affects the optimal progressivity of the income tax code. I find that the optimal tax code for an economy populated with altruistic households is approximately equivalent to a proportional tax of 23.1% with a fixed deduction of approximately $17,000 in 1990 US dollars. For an economy populated with non-altruistic households, however, these numbers are 18.8% and $12,000 respectively. This result implies that inequality is more severe in an economy with intergenerational links so that the policy maker requires a more progressive tax system to provide insurance. Additionally, I find that when the size of the government welfare program is chosen carefully, the additional insurance benefits from the progressive income tax code disappear"--Pages iv-v.