This question produced a little bit of controversy, so I check things out myself, using the caternary curve calculator, here:
http://www.spaceagecontrol.com/calcc...tton=Calculate

The actual curve will depend on how carefully you grade things, but if you grade them evenly, it should approach, at such a small displacement, a caternary curve very closely.

At the 4" dishing Dave suggested, the ∆length (change in the diameter of the pool) is only 1/4 of an inch. I don't think that would have any detectible effect on the pool.

Even at 8" -- double what Dave suggested -- the ∆ length is 0.07ft, or 3/4in. And, with an Intex metal frame or blow-up pool, I suspect you won't be able detect a 3/4" ∆ in the diameter of the pool at the top compared to the bottom.

But you have to be careful. It's possible that if you dish the pool 12", you might get a bit of wrinkling, depending on how elastic the Intex fabric is. At a 12" dish, you'd increase ∆length (diameter) by 2"; that might be a problem, especially if the fabric is very inelastic.