Difference in number of pages found and results displayed?

[Jbob]

When i type www.example.com (my site) in google search it says says 'about 2,400 pages found' However it only displays 146 results.

Similarly if i type example.com i get 15,000 results but only 176 are displayed.

Can anyone explain why it does this please? Are the unseen pages supplemental?
Thanks in advance.

[edited by: tedster at 4:58 pm (utc) on Mar. 13, 2008]
[edit reason] switch to example.com - it can never be owned [/edit]

[tedster]

The first issue you raise is the difference between a "with-www" domain name and a "no-www" domain name. They are technically different urls. More information is available in this thread [webmasterworld.com], found in the Hot Topics area [webmasterworld.com], which is always pinned to the top of this forum's index page.

Now on to the issue of the disappearing urls, with thousands promised and only hundreds actually returned. Yes, many times the missing urls are supplemental or duplicate. But there's more than that going on. It has to do with the way Google estimates the number of results, which is more challenging than you might imagine with a data-set as large as theirs is.

The original data is processed, tagged, and broken into shards that are stored in different spots. For example, notice that the cached pages can be served from a different IP address than the query results. As long as the number report includes the word "about", it really is just a best guess.

But it goes even further. These days, the shortened number of results has been getting mow and more common. Even a site: operator SERP mat not return all the urls that you find by searching site:example.com/directoryA/, site:example.com/directoryB/ and so on.

Why this is I'm not certain, but it is getting harder to see all the data about indexed urls. Maybe that's the whole idea, and maybe it's a side effect of other SERP changes that Google is doing. Possibly a bit of both.