In this dissertation, I study applied market design and incomplete information problems using microeconomic theory. In Chapter 1, I explore the determinants of matching-platform users' welfare. I show that the effect of changes in the platform's characteristics can be analyzed in terms of user competition and increased choice. My main result is that the interaction of competition and increased choice leads to a bell-shaped users' welfare function in their number of prospects. In Chapter 2, I study the private selective colleges' incentives behind their financial aid policies and their use of early admissions. I show that low-income students avoid the binding commitment of Early Decision programs because it halts their ability to compare financial aid. As a result, lower-endowment colleges use such an admission program to limit their financial aid commitments. Finally, in Chapter 3, I study the effect of the over-precision and inference biases in an investor's decisions. Using a real-options model, I show that the biases induce an overestimation of the volatility of the value of a project (VOP). As a result, the investor takes a wait-and-see approach: at the VOP that convinces an unbiased investor to invest, the biased one believes a more favorable VOP is likely and waits for longer.
