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Now, I know what you're thinking... "well, duh... the channels may not account for all ads."
Sure... makes sense (although my channels do account for all), except the impressions of all active channels (by date) are higher by the thousands than the aggregate data numbers. The clicks in the reports are slightly less (maybe .1-.2%).
I messaged Google about it, no reply yet. Anyone else seeing this? I setup my channels for each of my sites (by domain). What's interesting is that the increase I was expecting due to ad placement changes was more noticed in the numbers of the channel view.