I think it has to do with a person's metabolism and the style of clothing. sizes don't really matter, I think these small sizes tend to make you think you're thin when in fact you're not. Depends on your activity level and how your body burns off calories. Some people can go all day and still be on the heavy side while others stay small and eat junk food without a thought. I don't put much faith in sizes, if something fits and looks good on me, then I wear it.