Hijab has nothing to do with either. It is like asking a question: wearing trouser means decency or backwardness. Just like some people (actually most) prefer wearing trousers instead of shirts, some people prefer to cover themselves more (now we call that hijab). Hijab just means cover, and every human being has a right to cover themselves as much as they like although the right to uncover is limited. :D

I think it is just a matter a person's preference and their willingess to follow a religious injuction. A person can be indecent and still wearing hijab. A person can be decent with or without hijab. Backwardness also is completely independent.