Vanity sizing, also known as size inflation is used to refer to the phenomenon of ready-to-wear clothing of the same nominal size becoming larger over time.
eg. a size 8 dress can be a 34" bust or a 40" bust, or whatever the designer wants it to be This perpetuates women's fear of size and is part of creating a society where women are constantly unsure of their own image.
Men's clothing, in contrast adopted standardized measurement originally for military uniforms (where, for example, a pair of trousers with a 32" waist and a 32" inseam must be labeled as such regardless of who made it).
Sign if you want America to standardize women's clothing sizes. It's a small thing but it is an easy step towards women's equality.