CTR down while CPC and eCPM up, why?

[justawalker]

Based on reasonable impressions, we have the following record:

2009CTReCPMCPC
Q12.30%$4.040.17628655
Q22.30%$5.270.229469965
Q31.99%$5.410.272881356
Q41.69%$5.710.3396875

It says the CTR is keep dropping down, meanwhile we've got more and more high value ads, so the result seems not that bad, say the eCPM is not doing down.

But, we are worry about why the CTR goes down? One explaination we've seen on the web somewhere says "cos the users get used to the layout, so they understand that's ad, so they do not click on it". Well, if this is the whole reason, we do not need to worry about it, we even do not need to change the layout to somehow mislead the users to click on the ads. They know that's ads? Good, that what we want, if things go this way then be it.

On the other hand, we are thinking about one thing: what if the relevance of the ads dropped? This - on our understanding, is the worst thing we may image.

Any thoughts?

[justawalker]

re-format:

2009___CTR____eCPM____CPC
Q1_____2.30%__$4.04__0.17628655
Q2_____2.30%__$5.27__0.229469965
Q3_____1.99%__$5.41__0.272881356
Q4_____1.69%__$5.71__0.3396875

[ken_b]

More than a few of us are seeing the same thing and trying to figure out what's going on.

Here is a current thread with some of our questions and thinking:

[webmasterworld.com...]

[edited by: incrediBILL at 9:22 am (utc) on Dec. 20, 2009]
[edit reason] fixed link [/edit]