Essays in capital markets

Abstract

The thesis is composed of three chapters. The first chapter proposes that financial innovation induces endogenous changes in the composition of market participants, which can both increase the interest rate and reduce the risk premia earned on pre-existing assets. We consider an exchange economy with endogenous participation. Competitive investors can freely borrow and lend, but must pay a fixed entry cost to invest in risky assets. Security prices and the participation structure are jointly determined in equilibrium. We show existence and constrained optimality of equilibrium under general conditions, and then specialize to a CARA-normal framework with finitely many risk factors. The model reconciles a number of features that have characterized financial markets in the past three decades: substantial financial innovation; a sharp increase in investor participation; improved risk management practices; an increase in interest rates; and a reduction in the risk premium. In the second chapter, we study the effect of margin constraints on volatility and welfare in an intertemporal financial economy. We find that margin requirements do not necessarily reduce market volatility and can generate non-monotonic redistributive effects. The setup allows for full flexibility in setting margin requirements and is well suited to address regulatory issues. We study in detail two types of margin rules. The uniform rule, in which margin constraints are constant over time and states, and the practitioners' rule of tightening margin constraints in bear markets and relaxing them in bull market.

(cont.) The results are compared with the first best rule in which margin requirements are chosen just to prevent default. In the third chapter, we consider a framework with mean-variance investors that face margin and no short-selling constraints and can default on their pre-existing leveraged positions. Margin calls and portfolio rebalancing create spillover-contagion effects across markets. A negative shock in one specific asset can reduce prices of even uncorrelated assets with unchanged fundamentals. We test this result across different forms of margin contracts typically used in practice. Margin constraints can also generate a self-reinforcing mechanism that amplifies price movements and create discontinuity in the price schedule.