We study short‐maturity (“weekly”) S&P 500 index options, which provide a direct way to analyze volatility and jump risks. Unlike longer‐dated options, they are largely insensitive to the risk of intertemporal shifts in the economic environment. Adopting a novel seminonparametric approach, we uncover variation in the negative jump tail risk, which is not spanned by market volatility and helps predict future equity returns. As such, our approach allows for easy identification of periods of heightened concerns about negative tail events that are not always “signaled” by the level of market volatility and elude standard asset pricing models.

Agency mortgage‐backed securities (MBSs) with diverse characteristics are traded in parallel through individualized specified pool (SP) contracts and standardized to‐be‐announced (TBA) contracts with delivery flexibility. This parallel trading environment generates distinctive effects on MBS pricing and trading: (i) Although cheapest‐to‐deliver (CTD) issues are present in TBA trading and absent from SP trading by design, MBS heterogeneity associated with CTD discounts affects SP yields positively, with the effect stronger for lower‐value SPs; (ii) high selling pressure amplifies the effects of MBS heterogeneity on SP yields; and (iii) greater MBS heterogeneity dampens SP and TBA trading activities but increases their ratio.