[spearingthehead]

I tend to look at bi-modal as two bell curves that are close at a few parts, but not quite merging together, and tri-modal as three curves.

Wouldn't it be more sensible to treat each curve as one sub-category of the industry? It would at least make things more intuitive. My salaries tend to be in the bottom-most curve (55k was my top yearly income) and any changes in salaries in the top curve would probably have little to no effect on prospects at the bottom.