Burt presents argument and evidence for a structural ecology of social capital that describes how the value of social capital to an individual is contingent on the number of people doing the same work. The information and control benefits of bridging the structural holes - or, disconnections between non-redundant contacts in a network - that constitute social capital are especially valuable to managers with few peers. Such managers do not have the guiding frame of reference for behavior provided by numerous competitors, and the work they do does not have the legitimacy provided by numerous people doing the same kind of work. Burt uses network and performance data on a probability sample of senior managers to show how the value of social capital, high on average for the managers, varies as a power function of the number of people doing the same work.