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CTR from search engine traffic should be higher.
Just promoting in forums or news groups has usual a very low CTR.
Also please post the theme. Some themes like fan sites have usual a very low CTR.
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Knappster is right about the ToS. In the future, please refrain from disclosing statistics other than gross earnings.
If you haven't done so already, I recommend visiting the AdSense Tips page which will give you some ideas for optimizing your site:
Hope that helps,