Google supplemental index

The supplemental index is a secondary index for lower ranking pages and doesn’t contribute anything to your sites visibility on Google. Pages found in the supplemental index tend to be crawled less often and will never be assigned PageRank. As a result, these pages tend to appear lower in organic search results. There are many reasons why pages lose rank and fall into the supplemental index. Here are the most common:

• Low quality content or mainly images (1 line posts).
• Duplicate content from other sites. Beware of blogs as they create duplicate pages for archives etc.
• Identical page title or description.
• Orphaned pages – no or poor ranked inbound links.
• Lack of external links.
• Old and stale content.
• Excessive reciprocal links, linking to spammy neighbourhoods.
• The number of query string parameters exceeds Google’s algorithm.
• Too many pages, publish fewer but meatier pages.
• Cannonical issues causing PageRank to split (see below).

Doing a search in Google gives results from its “normal” index first, and then results from its supplemental index near the end. Sometimes, if not enough pages are available from the normal index, Google will include results from the supplemental results.

Calculating your supplemental index ratio

The The best way to calculate how many of your web pages is in the supplemental index is to work out the ratio as follows :-

Total Pages Indexed = site:www.yoursite.com
Pages in the Main Index = site:www.yoursite.com -inallurl:www.yoursite.com
Pages in Supplemental Index = Total Pages Indexed – Pages in the Main Index
Supplemental Ratio = Divide supplemental index by total pages indexed X 100

How to improve your supplemental index ratio

• Good quality relevant inbound links.
• Use a robots.txt file to stop search engines spidering irrelevant areas of your site.
• Remove or rewrite duplicate content (duplicate to your site and others (i.e. cut and pasted text from other sites).
• Create a Google sitemap.
• Lean and focused pages with rich content.
• Do not over seed your site with keywords.
• Unique quality meta description tags on each page. Otherwise Google will use the top text of your pages content and that may be navigation.
• Create original, compelling content, marketing it, and getting links you deserve.

Cannonical issues are causing PageRank to split

The sum of all inbound PageRank links to your site, is split between the total pages in your site. Thus a bigger page count, means lower average PageRank per page (depending on the site structure). A page with a low PageRank (minimum threshold ) ends up in the supplemental index. By reducing the number of pages you increase the average PageRank per url. Resulting in supplemental pages going back into the main index.