According to zjacob in Webmaster World, such changes seem to have certain characteristics:
- "Almost all of the changes seem to be due to external factors, so that in-site SEO does not seem to matter all that much. Knowing as to what that external factor is would be extremely valuable. DMOZ/Google directory changes do not fit the profile of the likely cause.
- The site's themselves seem to be evaluated on a site-wide basis for this (likely external) factor (which also means that there are sudden, dramatic changes to the rankings)
- The changes do not seem to have anything to do with so-called sandboxing factor."
In Digital Point forum, Jim 4767 says, "Increased by about 1.5K links. And no (to earlier poster), backlink updates are not done continuously on Webmaster Tools. They are a periodic event, but are done more often than the PR update/export."