I agree with Angie. If anything, I see that size numbers are now fitting larger than they used to. Of course, with some retailers, they always have. I remember when I was in my early 20's and consistently wearing a size 4 to 6 and Banana Republic's size 2 shorts were enormous. But because the vast majority of American women are now larger than they used to be, number sizes are fitting larger, too. That makes it next to impossible for a true size 2 to find clothing that isn't too big.
But like Aliona stated, clothing numbers run quite differently in other countries, too. It is absolutely possible that some things intended for overseas markets end up here, with what we consider wonky sizing.
But I find the same thing as Ledonna, except I don't thrift. At places like Marshall's or TJ Maxx, there are often things left because what is marked as a size small fits like a large. I go by eye more than number size in places like that because that is likely part of the reason some of those items ended up there in the first place.