Depends on sets, rests, rest days, diet, experience and whether your runnin any gear or not.
Just saying but all I do for back is
Deads 5x6
BB Row 5x8
Then on a differant workout day I do Underhand Chins 5x6-8
And back is my strongest and favourite bodypart and if you go on my profile you can see the sort of width I'v built since september. I find BB Rows are soley responsible for my middle back and lats, I alternate between a shoulder width grip and a close grip (like 6 inches apart). I think I have quite a good mind-muslce link with my back and using a cloer grip can really activate and squeeze the shit outta my lats but a wider grip lets me work my middle back muscles.
I dnot really count chins as back exercise cuz i get crazy pumps in my forearms and biceps from it...