You grab a pair of jeans in your normal size, but when you get to the fitting room, you can't pull them past your thighs. What gives? Shopping for clothes should be fun, but it's often confusing (and sometimes upsetting) with women's sizes varying so much from store to store. This Vox video investigates the reasons behind the disparity. One thing’s for sure: It’s not you; it's the store. So don’t feel bad (or surprised) if you're an extra small at one retailer and an extra large at the next.