How often Google Places updates?

[TheReachers]

Hi,

My first question in SEOMoz :). I have just finished doing citations and optimisations for a local business. I now want to know how often Google Places update their database to look for citations etc to improve rankings?

Many Thanks

[SangeetaC]

I saw ranking changed every week for the things. Google is very frequent as far as updations are concerned. Their are few updates as well like Panda update which it does periodically like in half year.