The norm to be thin-sociology?

Norms mean numbers, and is reflective of a particular society - in the fashion industry, among models for examples, it used to be considered the norm to be a size 2. With the likes of Nicole Richie, this norm is now bordering on zero and even 00, which is unhealthy and rather sick. In a given city (say NYC), fashion is highly influential, and the general rule is a size up from models - so the desired norm would be a size 2. However, the medical and healthy norm is size 10-12.