Second, although women and minorities have made significant advances into science’s professional ranks, there still are very few women and minorities among the scientific elite, i.e. Nobel Prize winners, members of the NAS, full professors, etc. Indeed, there is some evidence that a type of “old-boy-network” or “glass ceiling” exists in science when it comes to career advancement and prizes (Holloway 1993, Etzkowitz et al. 1994). Although there is nothing inherently wrong with relying on personal relationships to achieve career advancement, these relationships become a problem when they tend to exclude deserving people from a profession’s upper echelons. A principle of opportunity STANDARDS OF ETHICAL CONDUCT 59 implies that scientists should recruit, employ, and reward underrepresented groups, such as women and minorities.