Companies have been so focused on down-sizing to contain costs that they've largely neglected a looming threat to their competitiveness: a severe shortage of talented workers. The general population is aging and with it, the labor pool. People are living longer, healthier lives, and the birthrate is at a historical low. During the next 15 years, 80% of the native-born workforce growth in North America--and even more in much of Western Europe--is going to be in the over-50 age cohort. When these mature workers begin to retire, there won't be nearly enough young people entering the workforce to compensate. The Bureau of Labor Statistics projects a shortfall of 10 million workers in the United States in 2010, and in countries where the birthrate is well below the population replacement level (particularly in Western Europe), the shortage will hit sooner, be more severe, and remain chronic. The problem won't just be a lack of bodies. Skills, knowledge, experience, and relationships walk out the door every time somebody retires--and they take time and money to replace. And while the brain drain is beginning now, the problem is going to become much more acute in the next decade or so, when baby boomers--more than one-quarter of all Americans, amounting to 76 million people--start hitting their mid sixties. Based on the results of their yearlong research project, the authors of this article offer recommendations for gaining the loyalty of older workers and creating a more flexible approach to retirement that allows people to continue contributing well into their sixties and seventies. Companies can no longer afford to think of retirement as a onetime event, permanently dividing work life from leisure.