This study of a large sample of both urban and rural youth shows that 2.7% describe some level of discomfort with their birth gender. Interesting findings. Short article titled "Teen Gender Study Yields Surprises" is an interesting read.
http://e.startribune.com/Olive/ODN/StarTribune/shared/ShowArticle.aspx?doc=MST%2F2017%2F07%2F29&entity=Ar03101&sk=8B4431FA&mode=text