How often Google checks for duplicate content?

Question

I'm curious - I want to know does Google check for duplicate content everytime it crawls a web page or once in 6 months or so.

Do this checking similar to what Copyscape does? Wouldn't it be a big overhead, how does Google handle it?

Answer 1

They haven't said how often they do it so no one really knows. But their "Panda" algorithm has been processed three times which would indicate they accumulate information over a period of several weeks and then do a bulk update of their index based on their accumulated data.