We describe a rational expectations model in which speculative bubbles in house prices can emerge. Within this model both speculators and their lenders use interest-only mortgages (IOs) rather than traditional mortgages when there is a bubble. Absent a bubble, there is no tendency for IOs to be...

This article shows that the "risk premium" shock in Smets and Wouters (2007) can be interpreted as a structural shock to the demand for safe and liquid assets such as short-term US Treasury securities. Several implications of this interpretation are discussed.