I have the same AdSense ad unit on some pages twice and have noticed on a few occassions in the past month my page impressions are doubled. Clicks and earnings remain about the same, but CTR and eCPM are halved. It is as though sometimes Google only measures the fact there is one Ad unit on the page and other times it measures 2, which effectively means each visitor creates 2 page impressions. Has anyone else noticed this discrepency?