Formal i.e. white tie, semi-formal i.e. black tie, and informal i.e. suit, all have roots in 19th century customs subsequent to the replacement of the 18th century generic justaucorps, and has remained essentially fixed defined since the 20th century, despite decline following the counterculture of the 1960s. The 19th century frock coat rarely occurs except as formal alternative. For women, interpretations have fluctuated more dynamically according to fashion. For both men and women, hats corresponding to the various levels of formality declined following the counterculture of the 1960s.