Average # of post of the members hack

I was wondering if it is possible to have a hack that makes it possible to view easily the average number of posts per day of the members, and with that to delete ppl which have for example less than a X average number of posts per day. With such a hack it would be very easy to get rid of inactive and/or low-activ-members. Could someone make something like this? Because I was trying but without succes I think it would be a very usefull hack for more ppl...