With SharePoint 2010, Microsoft has improved the usage analysis and reports.
However, you may have the following issue:
after some months in production, especially if you have a high usage, data report are not generated for days (all value are set to 0).
No events are logged, while timer jobs related to usage analysis are running.
To have information about this issue, logon to the Central Admin and take a look at the SBPA reports (Review problems and solutions at the Monitoring section). You should have an item entitled Web Analytics: Monitors the health of the Logging Extractor component.
This happen if the staging database used by the web analytics service application is highly used.
To solve this issue, go to the Service Application management from the Central Administration and select your Web Analytics service application and click on the Properties button shown on the ribbon
Then go to the next step of the Service Application edition; do not change anything on step 1 (which is related to SA name and application pool used)
Edit the web analytics topology by adding Topology Database
Fill the SQL Server name and database fields
Click to the Next button to confirm the topology change
Et voiià, web analytics data should now be updated accordingly to the usage.