In Central Admin, you enable usage analysis processing in the logging and reporting secion in Operations.
Then you enable auditing on the particular site collection. This requires you to be a site collection administrator. You can configure it to track the following:
Opening or downloading documents, viewing items in lists, or viewing item properties
Editing items
Checking out or checking in items
Moving or copying items to another location in the site
Deleting or restoring items
Editing content types and columns
Searching site content
Editing users and permissions
Then you can run reports based off this information that it gathers for specific timeframes or by certain people.
It may be of use for you to investigate.