This dissertation studies how financial market volatility or uncertainty in the U.S. economy affects real economic activity both in the U.S. and other open economies. Chapter 1 critically examines a stylized fact about the effects of uncertainty shocks on the U.S. economy. A link between uncertainty and firms' investment, hiring, and production decisions has drawn much attention in contemporary discussions after the 2008 financial crisis. Bloom (2009) showed that uncertainty events, identified by spikes in stock market volatility, triggered immediate falls in output and employment, followed by rapid rebounds. I show that such stock market volatility shocks failed to produce this same pattern of responses after 1983. Chapter 2 studies the effects of risk aversion shocks, measured by increases in the VIX , on emerging market economies (EMEs). By estimating a structural vector autoregression (VAR) model, I find that, although risk aversion shocks do not have much impact on U.S. output, they do have a noticeable impact on the output of EMEs. To explain the contrast between the impact of risk appetite shocks on EMEs and the impact on the U.S. economy, a credit channel is proposed as a propagation mechanism. In the model, an increase in the VIX is translated to a risk-aversion shock that generates a "flight to quality." As international investors pull their money from EMEs, borrowing costs increase and domestic credit falls as a consequence of credit market imperfections. Higher borrowing costs, in turn, lead to a fall in investment that causes a real depreciation and a decline in total output through sectoral linkages. Finally, Chapter 3, which is co-authored with Prakash Loungani, studies the effect of uncertainty shocks on unemployment dynamics by separating out the role of aggregate and sectoral channels. Using SP500 data from the first quarter of 1963 through the third quarter of 2014, we construct a separate index to measure sectoral uncertainty and compare its effects on the unemployment rate with that of aggregate uncertainty in a standard VAR model, augmented by a local projection method. We find that aggregate uncertainty shocks lead to an immediate increase in unemployment, followed by swift reversals. In contrast, sectoral uncertainty shocks have a long-lasting impact on unemployment, with the peak impact occurring after two years. Our findings highlight an additional channel through which uncertainty shocks have persistent effects on unemployment by requiring substantial inter-industry labor reallocation.