It's Martin Luther King Jr. Day, which has us thinking about the state of our nation — specifically, the state of diversity in our nation. It's a complicated subject, to be sure, so to help us think through it, we're joined by Adia Harvey Wingfield, a professor of sociology at Washington University, whose new book, "Gray Areas," examines why racial inequality persists in the workplace despite today's multi-billion-dollar diversity industry and what actions we can take to create an equitable, multiracial future.