How often does Google update pagerank?

Answer 1

There are two types of page rank. One that we normally see and use is called "Pseudo Page Rank". This is the one that is publicly available form Google in tool bars or through other sites that use the Google approved code to track page rank. This page rank is updated in approximately 3 months. It could be earlier or late as to the liking of Google guys.

The actual page rank is how ever only available with Google and changes dynamically. No other body on earth knows the real PR value. This can be any thing like 3.124 or 2.789 not necessarily a whole number like 3 out or 10. When there is a Google PR update this decimal values may be rounded up and exported for public use. Again the rules of rounding is not available with anyone except Google.