This dissertation consists of three chapters about how access to financial markets and composition of the labor market determine aggregate macroeconomic outcomes. The first chapter examines the macroeconomic consequences of credit uncertainty using a structural vector autoregression model with stochastic volatility (SVAR-SV). Credit supply conditions in the U.S. is captured by the banks' reports on how credit standards for approving loans have change over time (Bank Lending Standards). The empirical analysis shows that the volatility of macroeconomic and financial variables rises in response to an increase in the credit uncertainty shock. The economic activity falls and credit growth and related interest rates decrease persistently. Moreover, credit volatility shocks explain around 10% of the FEV of endogenous variables. A dissagregated analysis shows that the effect of these shocks are mainly explained by their effects on the corporate business sector. The second chapter studies the role of time-varying credit limits through the lens of a life cycle incomplete markets model calibrated for the U.S. Changes in credit card limits are explained by observable household characteristics and the estimated unobservable variation is quite large. The quantitative exercise shows that even though young households are more indebted in an economy with stochastic borrowing limits, aggregate consumption is not greatly affected by transitory or persistent shocks of this type. However, in the presence of these shocks, households lose the ability to self-insure against other uninsurable idiosyncratic shocks, e.g., labor income shocks. A disaggregated analysis shows that the loss of self-insurance capacity is mainly explained by the effects that stochastic borrowing limits have on the wealth distribution, the precautionary savings channel households have to face unexpected risks. The third chapter studies the role of informal markets to explain economic and demographic variables during a pandemic. The quantitative exercise shows that lockdown policies are less effective in economies with large informal markets, infection and death rates will not decrease as much as formal economies. Moreover, the size of the recession would be exacerbated because informal activities are not counted in the calculation of the GDP. To generate similar results to an economy with only formal markets, the economy with informal markets must implement more severe containment policies.