When should I allow my Teenage daughter to wear a thong?

I found a poll asking at what age would you let your daughter wear a thong. Although my daughter is just getting to that age, I feel it is an important issue which many parents have an actual opinion on it. I would love to get the personal opinion of different parents on this subject. So at what age you think a daughter should be able to wear a thing? You can vote on the poll here: [url=http://pollsb.com/polls/poll/2031671/at-what-age-would-you-allow-your-daughter-to-wear-a-thong]Poll: At what age would you allow your daughter to wear a thong? - polls survey[/url]