Any student studying introductory economics could tell you about traditional concepts like efficiency, production functions, and others. But there's one essential concept that's often glossed over: economic inequality. As part of our Marketplace Crash Course series, we spoke with Homa Zarghamee, professor of economics at Barnard College, about inequality and why it's important to learn about. And, a look into why the Fed chose to raise rates by a quarter-point yesterday.