1 = 100
2 = 150
3 = 175
4 = 187,5
5 = 193,75
6 = 196,875
etc...
In this example the effect is halved; in reality it will be more complex, but for the purpose of this demonstration it shall suit.
Therefore I see the difference between 5 and 7 not to be the same as between 3 and 5. It is indeed smaller.
copied from: http://buzzerbeater.wgz.cz/coach-lvl-affect