This paper documents the fact that in options markets, the (percentage) implied volatility bid-ask spread increases at an increasing rate as the option's maturity date approaches. To explain this stylized fact, this paper provides a market microstructure model for the bid-ask spread in options...

This paper reviews the literature on credit risk models. Topics included are structural and reduced form models, incomplete information, credit derivatives, and default contagion. It is argued that reduced form models and not structural models are appropriate for the pricing and hedging of...