This dissertation consists of three chapters on monetary policy, R&D investment, and test of corporate capital structure theory. In the first chapter, I examine the impact of large-scale asset purchases (LSAPs) on corporate financing and investment. I find that LSAPs increased corporate financing and shifted the corporate financing pattern towards greater equity financing. Specifically, LSAPs enabled noninvestment-grade firms to issue more public equity and allowed investment-grade firms to issue more bonds. I find that LSAPs also affected the stock market through the portfolio balance channel. With the reversal of flight to quality, noninvestment-grade firms enjoyed significantly higher stock returns than investment-grade firms. After rais...