In 2008, when the housing bubble burst and the global economy crashed, policymakers were caught flatfooted. Despite months of worry and concern about a housing bubble, signs of financial institutions on the road to crisis, and the possibility of a major economic downturn, they scrambled to put together an emergency response package. They struggled to understand the interconnectedness of the mortgage markets and the different parts of the financial system. And they had few “off the shelf” ideas