One such factor a search engine uses to determine a sites relevance is keyword density. If you think about it logically this of course makes sense. The more times a phrase appears on a page the more likely the page is to contain information on that search term. Keyword density can work against you however if you place the phrase on your page too many times. This is known as keyword stuffing and in a blatant spam technique.

What can keyword density tell us?

Keyword density is not the deciding factor on how your site will rank however it can tell you something. If the word isn’t on the page at all then you probably won’t rank for that keyword. If your keyword isn’t in the title it will be harder to rank for that search term. If you put your keywords into the header tags this could help. The density is not the only thing but how close to the top of the page the phrase appears and how far the repetitions of the term are spaced.

There are however plenty of SEO agencies who will tell you keyword density is not considered by the search engines. Take the search term ‘SEO Agency’ I did an analysis on the top 4 organic ranking sites here is what I found:

Keyword density for silverbean is just 0.71%

Keyword density for further is just 0.83%

Keyword density for further is 3.60%

Keyword density for scottdsmith is 0%

The results are very interesting as for website 4 the term does not even appear on the sites home page, title or meta inforamtion. It appears the keyword density of the title is very important, as the top 3 results have a higher density in the title, although the site in position 4 has a title density of 0%.

So what could explain their inclusion in the top 4 positions? It must be many factors, not just keyword density, which has an impact. Synonyms must play a big part in ranking as website 4 does not even include the target term on the home page. I would suspect backlinks play a large part in website 4 ranking so highly as a large amount of backlinks with the target term in would signal to Google the website is relevant for the term. This is a brief analysis and further research will need to be done to draw some conclusive findings.

As part of any comprehensive SEO strategy this type of analysis of the keyword density of your competitors will help you to understand how you could tweak your own activity to improve your rankings. There are many excellent tools which will help you to create the data you need to be a more effective SEO. One free tool I can recommend is SearchStatus it is a Firefox plugin which will show you some interesting metrics.

So the consensus is rather than focus on keyword density you should make sure your pages read well. Don’t try too hard to get your keyphrase into your copy. The most important thing is to have interesting content for people to read. If it's interesting then people will share and link to it, which is probably still the most important ranking factor.