We notice a trop in adsense clicks and revenue in May, June and July which is almost the same amount as the percentage of total returning visitors. In our case increment of returning visitors is from 15% to 20% for the last 3 month and 10% to 20% for the last 8 months.
Only 10% of returning visitors are direct visitors but about 60% come back using our main keywords others are from several sites.
Could this be a click fraud algo to prevent from organized clicks? Has someone similar results?
(no we are not involved in any network)