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For my target keywords there are only 10-15 active advertisers on AdWords; so any publisher joining AdSense with a portal on our subject matter is going to exhaust well targeted ads very quickly.
I think you need a very busy site with many new visitors daily to make it work.
On the other hand, they are tracking the traffic flow and found more and more "targeted/optimized sites".
I do not think that Google has lowered the payout rate yet. If that would happen sometime, we could see much lower revenue.
I have a feeling that some advertisers with high CPC campaigns had pulled out Adsense program because after 40 days, they had not seen the expected ROI (conversion rate).
Most Adwords advertisers know nothing about Adsense. They have their budgets, their campaign timings, their own agenda.
I think you have picked up some nonsense from a spammer on another thread and you are running with it.