I think sizes nowadays are all over the board. I can wear as little as a 0 in petites, although I'm a 2 or 4 most of the time, depending on the cut and style of the jeans or pants. I can fit into a size 5 in juniors, and even XL or 16 in girls -- if the style is loose.
Lee jeans fit me best. Also some of the pants by Petite Sophisticates and the petite department at Talbots. Just enough room in the butt area to accommodate what's there without the extra fabric sticking out in the hip area. The waist, however, is still loose. I've never found a pair of jeans that fit me right in both the waist and butt/hips. I settle for the pair that fits right in the butt/hips AND with the LEAST amount of fabric hanging from the waist. This way the waist doesn't have to pucker and bunch too much when I wear a belt.
I wish I can just go to a store, see what I like, find it in a 4P, take it home and have it fit. Every darn time I go pants shopping, I have to try on every pair. It's a PAIN especially when you're dragging a 4-year-old around.
Pinky