i found this in the hub pages help page.
The easiest way to keep track of your Google Adsense earnings on HubPages is to create a channel URL in your Google Adsense account. This will allow you to seperate your HubPages earnings from your other sites.
Log in to your account at https://www.google.com/adsense/
Click the Channels link below the AdSense Setup tab.
Choose the AdSense for content sub-tab and click the URL Channels link
Click Add new URL channel, and in the resulting text box, enter the URL that you would like to track (use "hubpages.com" to track all of your impressions on HubPages)
Click Add channels.
The new URL channel will begin tracking data almost immediately.
just visit this for more info. http://hubpages.com/faq/#track_adsense