There are top scoring pages with not a single occurence of the key phrase. To me, that ends the KW (requirement)discussion.
That's anchor text not keyword density. I still scratch my head after reading the posts from people who insist that one factor will get position in the SERPs. I've said it before and I'll say it again...It's a combination of factors. Actually it's a combination of around 100 factors. Google just won't say what they are.