Do Multiple Adsense Units reduce CPC?

There are several current threads on this topic - it might have been an idea to have posted to one of them rather than starting yet another one :)

Anyway, my experience.

A while back I decided to add a second block to my best paying page. Did a bit of page redesign to make it look good, and hopefully get a few clicks.

Bottom line is that the second block very rarely got any clicks. As each time a block loads it counts as an impression, the ctr basically halved. At first there was no appreciable difference, but after a couple of weeks I noticed the epc starting to slide. I deleted the second block, and ctr returned to normal, along with epc a few days later.

The other thing to be aware of is 21_blue's recent posting on the chain reaction that may be started by having cheap MFA's appearing on under-performing extra ad blocks.

thank you david for sharing your experiences.

has anyone else tried the same thing ?

thanks.

labnol,

You'll find this thread interesting.

[webmasterworld.com...]

As each time a block loads it counts as an impression, the ctr basically halved.

david_uk: I noticed that you have said this many times now. But in my experience, the CTR only decreases for multiple ad units if you show the data "by individual ad unit" and not "by page" in the advanced reports section of AdSense.

IF you stick to the default "by page" reports, nothing should change b/c of the additional ad unit. CTR should actually go up due to more possibilities for users to click.

I noticed that you have said this many times now. But in my experience, the CTR only decreases for multiple ad units if you show the data "by individual ad unit" and not "by page" in the advanced reports section of AdSense.

But surely if you are getting a load of extra impressions on the page, unless they are getting extra clicks the ctr will go down? If you get say, 400 impressions and 40 clicks then you add an extra unit, if your clicks stay the same and you double the impressions you also half the ctr. Or am I missing something here?

The reason I have repeated it is that it is my personal experience. For some reason, the vast majority of my earnings come from my main index page banner. There have been times when I have very few other banners. They come and go. At the time I last experimented with this, I had a couple of banners running as well as the big earner. Putting the extra banner on virtually halved the site's ctr as it got hardly any clicks. I know that many people's earning have a much more even spread than I do.

IF you stick to the default "by page" reports, nothing should change b/c of the additional ad unit. CTR should actually go up due to more possibilities for users to click.

Sorry - don't follow the logic here. If you look at the site-wide statistics, adding extra impressions leads to a lowering of CTR unless the extra units get their fair share of clicks. The fact you have extra units doesn't mean that you will get extra clicks - wish it did :(

Thanks for clearing this one up :) I've been using the by ad unit ctr for so long for the reason above that I'd forgotten the by page option offered a different figure.