Kudos for pointing out that it's the shape of the distribution that matters, not how far apart its endpoints.

Interestingly there are articles out there which suggest that one distribution (of competence, rather than productivity, but intuitively you'd expect the two to be related) is actually bimodal rather than normal, "the camel has two humps":

http://www.codinghorror.com/blog/2006/07/separating-programm...