I find that sizes on clothes are all over the place. YOu can't even really tell a true size, you just have to try items on. I also think depending on the quality of the clothes size will vary. I bought a pair of namebrand pants out of Marshalls Josephine Chaus, size 4, I bought a pair of cords out of the Express size 6, and I have jeans out of the gap, size 8, (they fit in the butt but too big in the waist and they are too slim in the thighs).
It's frustrating, so my size ranges from 4 to 8 depending on where I shop. I think they are making clothes for skinny white girls, with no thighs and wide hips and white shaped butts.
Tim Gunn of Project Runway said in his book that sizes are larger now than they use to be 20 years ago. A size 4 is really a size 6 when compared to clothes sizes before.
He also said that true sizes are haute couture fashion sizes.
I find that living in NYC, there are a lot of teeny tiny sizes. Size 0, and 2. There are a lot of bony skinny women in NYC. I'm slender but I'm not bony, my collar bones won't cut cheese.