Companies pay disproportionately high salaries to CEOs and other high-powered professionals willing to live and breathe their jobs, on-call 24/7, ready to pick up and travel. It's a phenomenon Harvard historian and economist Claudia Goldin calls "greedy work" and she says it's a big reason why the pay gap between men and women persists -- because the people typically tasked with caring for kids, the house, or elderly parents simply can't put in as much time and energy at the office. However, she notes, there are signs of change, with younger generations demanding better balance.