At 126 (pre-Atkins) I had four size 8 petite pants that I could wear. Rolls above the waist, and I wore loose size medium tops to hide it.

Now, at 113 I can wear new size 4 petite pants, but I cannot fit into size 4 petite pants from my closet that I bought years ago. They are definitely a slimmer cut.

Somewhere in the last few years, I think all the sizes got "promoted". We were getting bigger and buying a larger size was so depressing, the manufacturers re-labeled the clothes so we would buy more without admitting we were larger.