I've found that my size can greatly fluctuate depending on which designer and department I buy my clothes from. In "trendy" young adult/teen clothes, I've found that I often wear a 12, except for A&F and Old Navy, in which I wear a 10. However, in my professional/business clothes, which are targeted to a more broad audience, I've found that I can wear an 8-10 in some of the pants, and even as small as a 6 in some shirts and skirts. In trendy clothes, I wear a Large for fitted tees, but in more professional/"grown up" clothes, I tend to be more of a medium and occasionally even a small.
So... does anyone else notice the semi drastic size differences in correlation with age? And what are your philosophies behind it? Is it to keep older ladies feeling like they haven't gained an ounce since their teenage years, or to maintain body dysmorphia among young women?