For my content sites, I'm happy if I get .5 CTR. Anything higher is a miracle and a one-in-a-month day. That's why traffic is so important. The more you have, the more that .5 click generates, the more you make.
When making a webpage and taking in mind that this page must bring some profit I place adsense block to get around 12-19% CTR. Of course you have to make an appropriate design and think as your visitor to attract his attention with ads.
If average visitor gets 10 ~ 20 page views, which is likely in any content site, then .5% ctr means 5% ~ 10% ctr / visitor - which is not bad.
Hmm, if I can achieve 7%-10%, there is no reason other people can't do the same with similar ads placement like mine. The key is to put the ads on the hot zonal area of the page.
There can be lots of reasons why other people can't do the same. First, they may not be getting relevant ads - which may entirely be Google's "fault" rather than theirs. Put up a site about something that they just don't have advertisers for and you won't get good ads. The same thing is true if there are only a few advertisers whose ads your visitors have already seen ten thousand times at every other site they've been to - you'll be lucky to get any ctr at all. Secondly, your visitors may be flat uninterested. Let's say you write about high priced automobiles, but you do so in a humorous and engaging way that attracts a lot of visitors just because you are funny and they love to read your stuff. The ads would be great and might have a wonderful ctr if your traffic came from search engfines, but instead it comes because people just love your writing and have no real interest in expensive cars at all. Low interest = low ctr. In general, traffic from search engines is more likely to generate ad clicks than "subscriber" traffic. That's partially because the people from search engines are "searching" - they want info about something and an ad on your page may be very interesting to them. On the other side, your "regulars" may generate very few clicks, both because they are here for a different reason and because they have already seen the ads that run at your site (assuming your subject matter tends to draw the same ads week after week, and that's often true for focused blogs). For most sites, 2% over-all is a much more reasonable goal, and 1% isn't necessarily a sign of failure on your part. To really know if you are under-performing, you'd have to compare yourself to a similar site with a similar visitor mix and similar popularity. As none of us are allowed to actually come out and say what our CTR is, that's pretty hard to do. Absolutely DO experiment with placement - it can affect your CTR. But don't expect miracles - there are a LOT of factors here.