Stealing some info from the Utopia Talk thread, I had to change from exponential to a polynomial description... Obviously this can't be right because it starts to curve back up eventually- but it should be fairly accurate up to at least the point where X = 180. This 180 value represents 90 (ninety) Professors over the category's cap... If you get substantially beyond this point let me know :P
Y =[1.9*(10^-5)]X^2 - [6.35*(10^-3)]X + 1.02
Where;
X = # of Skill Points above the cap of the category in question
Y = The effectiveness of the category in question