What causes your PR to drop?

What determines if Google should lower or raise your PR? We had a PR of 4 and after this last dance it is now a PR3? Can this still change since the crawl has taken place?

Also when we had a PR4 we had no BackWard Links and our site has a ton of quality links? We started a webmaster tool site and our main page on that site has a PR4 with a back link and its only a 2 months old.

I appreciate your input...

I'd be interested to know this, too, having had a site with PR6 drop to PR5, although I'm seeing a small increase in back links.

Only difference I can think of is the increase in outgoing links on my homepage to external sites -- I had 3 new links going out to new sites, and I'm wondering if this could affect my PR, since only one of these sites is indexed so far - the other two have no PR at all. Did I just make a major mistake???

I think Google is getting more aggressive in PR definition. Everyone tests link:www.yahoo.com. Did you notice that it has dropped from 692,000 to 661,000 backward links. I doubt that there are fewer web pages; so my guess is that, on the whole, Google is becoming much more agressive in its PR definition.

So a site that would have been PR6 last month, may have dropped to PR5.

The scary thing...it also seems to me that pages owned by individuals are dropping in rank, while only institutions are increasing in rank. I've noticed that there used to be a good number of pages by small organizations intermingled in search results for Salt Lake. Now, only government and big organizations show up in the first several pages of search results.

It looks to me like Google has added pr zero to the range now for all sites so that has lowered the threshhold. I am seeing this on many top sites even.

A general decrease across the board normally reflects that Google has crawl a large chunk of new web pages.

PageRank calculated across the mass of pages Google has index or the Internet Universe as Google know it.

As such... if new links are not consistently added to your site at the rate Google's Universe grows a decreasing trend will be the norm.

Local causes... also affect this -- a good link that you had previously may have been down (server outage) at the time of the crawl, a previous linker removed the link, your own site was down and a few dozen other reasons.

Keynote: if ranks stayed the same or increased -- nothing to worry about... everyone else in your competitive area decreased as well. If decreased in ranks -- look local for the cause.