This dissertation focuses on a major challenge to asset pricing theory: the valuation of mortgage-backed securities.

In the first chapter of this dissertation (with Mikhail Chernov and Francis A. Longstaff), we develop a three-factor no-arbitrage model for valuing mortgage-backed securities in which we solve for the implied prepayment function from the cross-section of market prices. This model closely fits the cross-section of mortgage-backed security prices without needing to specify an econometric prepayment model. We find that implied prepayments are generally higher than actual prepayments, providing direct evidence of significant macroeconomic-driven prepayment risk premiums in mortgage-backed security prices. We also find evidence that mortgage-backed security prices were significantly affected by Fannie Mae credit risk and the Federal Reserve’s quantitative easing programs.

In the second chapter, I study the relationship between funding liquidity and the valuation of mortgage-backed securities. Most of the financing for mortgage-backed securities occurs through a trade known as a dollar roll, the simultaneous sale and purchase of forward contracts on mortgage-backed securities that is analogous to a repurchase agreement. I develop a four-factor no-arbitrage model for valuing mortgage-backed securities that allows for the valuation of dollar rolls. Unlike previous models of the dollar roll, I allow for the possibility of a prepayment risk premium. I develop a new measure of mortgage specialness that is independent of prepayment risk premia and agency credit spreads. I find that specialness is related to measures of balance sheet constraints and primary dealer positions in mortgage-backed securities.