Besides bow length to draw length I'd also materials used.

But, I'd really have to say that the design of the bow also has a lot to do with it. For instance, I have a 68" Brack (60#'s at 29") that is very smooth to my 29" draw. But I also have a Bob Lee 60" that is made 61#'s @ 27". The Lee is extremely smooth and does not stack at all. I have a 60" Bear that is 45#'s at 28" that stacks like crazy on me.