It’s a known fact.  The search engines like good, original content - and for the most part, large sites.  So, as you build your rankings, you will want to keep track of how many pages on your site that are indexed in Google.  This is actually, a very simple process.  You can check it out in Webmaster Central.

Or, you can simply go to the Google command line and enter site:www.[name of your site] .com .  You will get the total number of pages.  For example, I did a query on MommyAdvisor , one of my sites.  I have 18,100 pages indexed in Google.

From there, go to the bottom of the results and click on the last page of the results.  It is my own personal belief that any of your pages that are not presented after that page - it is a darn good chance that they are in the supplemental index.  Now, if you know what I am talking about, you are saying, "but, I thought that Google abandoned the supplemental index ".  Officially, yes, but, I still believe that their is some distinction in place for less significant pages.  And, if you are seeing that a considerable number of your pages cannot be seen, it is time to build some links.  Look, the supplemental index did not go away… Google just made it harder to find those pages.