I do not think keyword density is very important. I like to put my keywords in the title tag and the h1 tag, and then mention them a few times in the body text. I dont think you need to worry about a particular density though.
For the main keyword, 2% to 3% will give good results. With lots of related keys at low percentage rates the results are impressive.
I have always been told to keep it below 2% that would give plenty of scope to introduce a number of keywords several times in a 500 page article
I think keyword density is not more than 10% for search engines friendly websites. insurance colorado
I think keyword density directly depends on the number of words in the article or the length of the article.