How Many Words in a Young Adult Novel?

I’m working on a young adult novel and the most publishable book length is a question I have been researching.   I will be posting on ‘optimal YA novel length’ for several days. I would love to hear what you have discovered, too, so please use my comments block to tell me about your experience with YA novel length.

One answer from Writers Digest is a simple spread:  55,000 – 69,999 words.
Resource:
WritersDigest.com: Word Count for Novels and Children’s Books: The Definitive Post: Chuck Sambuchino: October 24, 2012
http://www.writersdigest.com/editor-blogs/guide-to-literary-agents/word-count-for-novels-and-childrens-books-the-definitive-post

My novel is historical, and I am wondering if the rules change for contemporary fiction including romance, or science fiction, or dystopian, or any other genre.