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This makes the site more sluggish because the database is under a heavy load, pages loading a bit (lot) slower than normal, but overall it's not the normal snappy response when we're doing this type of maintenance work on the live site.
We used to do it late at night to avoid such sluggish site problems but it was unavoidable this time, had to happen during prime time.
Well, of all the amazing things to happen, AdSense CTR actually increased, along with revenues, during this maintenance cycle!
Just speculating but perhaps people got tired of waiting on the longer page loads and used AdSense as an escape route.
Earn more, bog down your server today!
Just kidding, somewhat, but I thought the visitor behavioral observation was interesting at a minimum because we've read reports from people that upgrade to faster servers and income suddenly dips so maybe too much site performance is bad for AdSense performance?
If your site is slow, less people are likely to bookmark it and return to it in the future. Less people are likely to recommend your site or link to it from their own sites. So in a year's time, your CTR will still be high, but your page views will be lower than what they would have been and therefore your revenue will be lower.
[webmasterworld.com...]I think Google have tweaked their algo to discount "quick clicks".
Sounds reasonable to me, too. Who knows--maybe they have a publisher "quality score" that factors in things like time spent by clickers on an advertiser's site compared to the publisher average for a given ad, advertiser, or whatever. (That's just speculation, of course, but it fits in well with the philosophy behind "smart pricing.")