I sincerely believe that most webmasters and web designers have a misconception about the keywords density .
There is a parameter that we can not control, and yet will determine the influence of this factor.
This parameter is simply the search engine itself, each engine has its own algorithm to calculate the value of the density and take it into account for the ranking.

The only way to really know if your strategy works is to try.
Make adjustments to observe the different changes in your website ranking on search engines .

Choose 2 search engines: Google and MSN, for example, to mention only the most important and conduct your tests.

For my part, I noticed huge changes over time regarding the “title” tag and how the different engines take into account.

Play around with the structure, the content and the number of keywords in the title and observe changes.
Change the number of keywords in your page body content  in the same way.

Working on the Keywords density is a task that requires patience and time.

Tip:
Prefer meta tags rather short, too many keywords in the meta tags may penalize you in the search engines.
Select precise key phrases specific to your site to set yourself apart from the competition.
Create content for humans and not for search engines.