What is the most important price in the economy? Betsey Stevenson and Justin Wolfers say that it's the interest rate, and they dig into where it comes from, and how it drives all spending in the economy. These big ideas yield a framework called the IS-MP model which policymakers use to help devise fiscal and monetary policies to kick-start the economy. Co-host: Nastaran Tavakoli-Far. Editor: Alastair Elphick. A Modulated Media production.