Dean Jones says:

"I'm not playing your 'numbers game.'  You know full well that I came up from the 25th percentile to the 33rd and now I'm at the 47th.  I've already moved up far more than three percentile levels! 

Tell me:  Why should I move up to the 50th percentile?  Give me one good reason!"

Your response:

1.  "I'm agreeing to teach five days a week.  Many professors teach only two or three days a week.  Shouldn't that prove my dedication?"

2.  "If you won't then, I am sorry, but your salary offer simply won't meet my requirements.  I may even have another offer that is more than adequate.