Yeah, like others on this post, I think 2% is an effective level of keyword intensity. I don't write copy scientifically or systematically checking my density, though. Well-written copy will naturally hit within the parameters that users will find useful and Google algorithms eat up.
I wouldn't worry too much about keyword density. Just write the unique article for the content you are focused on. You don't want to keyword stuff, so just make sure it makes sense and is written well.