"In France, hair trends are a matter of generation," Matthieu Séguier , hairstylist and owner of Paris' Salon Séguier , told me this fall after giving me what he affectionately refers to as "the French girl haircut." That is, the collarbone-length, slightly A-line , layered cut that is flooding the streets of Paris right now. "People in their 30's saw their mother with short hair [in the '80s], so they want their hair longer," he explains. "But their daughters will return to shorter lengths."