[ffusco]

In any group there will be a bell curve of distribution reagrding any trait you can imagine. A persons individual genes will obviously determine his or her potential for certain traits.

[Doctor Stochastic]

In any group there will be a bell curve of distribution reagrding any trait you can imagine.

Income?

It would be true if there were effective upper limits or if no individual were to dominate the population. Heights and weights cannot be on a bell-curve (normal, Gaussian, etc.) because there are no negative heights (but for the most part, heights and weights do lie close to such a curve.)