Surely there must be some common traits that your candidates all possess?

I think that's true. They don't look alike, but at the sub-structure they share some broad common qualities. Over the years I have boiled down the general characteristics we are looking for to these three categories: Hunger, Speed, and Weight.

Hunger is fantasy about the self, dreams that a person is prepared to risk in the real world. Everybody has fantasies. Everybody has dreams, but only some people act them out. Hunger, as I use it, means that you're willing to take risks, that you're willing to fail. It is the failure that teaches. We learn from our success but we learn more when we fail. There is no safety net in the positions we are trying to fill, and we want someone who has been swinging on that trapeze for a long time.

Speed means intellectual agility, the capacity to learn "foreign languages" quickly, whether those languages are finance, organizational development, or biotechnology. We look for learners not teachers, people who can listen and synthesize rather than lecture -- people who ask a different question.

Finally, weight means the capacity to use formal and informal power wisely, for moral ends. A heavyweight gets things done, and does it in a way that serves the purposes of the organization and raises its ethical aspirations. Most heavyweights are older; they "gain weight" through experience, but I have met younger people with weight. They understand their power and they understand its use.