What's up with the site: query?

It bounces back and forth every few days...

[birdstuff]

There is something strange going on and I can't figure out what it is.

When I type site:example.com into Google it lists 1500+ pages about half the time. The other times it lists around 1000 pages. This has been going on for a couple of months now.

The query returns 1500+ pages for my main site (the correct amount) for a few days then around 1000 pages for a few days, then back to 1500 again.

Rankings and traffic don't be appear to affected by the number of pages listed.

Any ideas on why this is happening?

[Marcia]

Different data centers, more than likely. Try accessing some by IP number for several days straight, see which correspond with the differences you're pulling up with regular Google and notice if you see changes on those.

[birdstuff]

That's what I'm thinking too Marcia, but the swing of almost exactly 500 pages switching back and forth for 2 months seems very odd for a typical difference between datacenters.

[uncle_bob]

I think google can give odd results sometimes, a search for site:example.com returned X results, and offered to search for just the english pages. Clicking just english pages it returned 2X pages!?!

Sometimes I think google is just having a laugh with (at) us!