That kind of CTR is unusually high, and may well trigger a manual review. Why would 40% of your visitors click on Adsense rather than visiting another page on your website? Do your pages have much content?
wow if i get 40%, I'd quit my day job. Mine is 1.5%. After experimenting for over 2 months with different colors, layouts and locations, I was able to increase my CTR from 0.75% to 1.50%. But whatever i do, I'm not able to increase my CTR above 1.50%. I get over 1500 uniques per day, mostly from google
I have a .02% CTR. But I use a text-rpg game so users are always busy with other things. And it is a small ad. Around 30k impressions/day.
40% or any high ctr usually occurs on low traffic sites in my experience. when traffic goes up ctr usually goes down.