incrediBILL - 2:39 am on Apr 27, 2010 (gmt 0)
The reality is that even if 50% of your users tomorrow will install Adblock, statistically speaking, your AdSense CTR will not be affected.
That theory depends on whether those people installing AdBlock tomorrow never clicked on ads in the first place.
People also install AdBlock to protect themselves from 3rd party ad servers that every now and then get hacked and start attempting to serve up malware instead.
If that group of people were previously prone to click on AdSense then off course your CTR would go down as you lose people that were clicking.
Just like I had a drop of MSIE by 17% that had a 4.79% CTR, how can anyone say there was no loss of income when that 17% got replaced by 3.6% CTR and lower.
Obviously AdSense is subjective and they may push more high paying ads first which would somewhat balance things out, assuming those people were on high paying pages in the first place.
Let's do some math here...
Assume all clicks from MSIE or FF clicks pay a dime $0.10
Then assume out of every 1,000 visitors 4.79% of them click, that's 47.9 clicks, on an ad that pays one dime per click, or $4.79.
Now assume we get 100K visitors a day so if 68% are MSIE, you earn $325.72.
100,000 (visitors) * 0.68 (MSIE%) * 0.0479 (CTR%) * $0.10 (DIME) = $325.72
Compare that to 51% are MSIE visitors, the same traffic would only earn $244.29
100,000 (visitors) * 0.51 (MSIE%) * 0.0479 (CTR%) * $0.10 (DIME) = $244.72
OK, so you got 17% new clickers in other browsers that have a 3.6% CTR, all clicks are a dime, per 1,000 visitors you would earn 36 clicks or $0.61. or $61.20 per 100K visitors.
100,000 (visitors) * 0.17 (OTHER BROWSER%) * 0.036 (CTR%) * $0.10 (DIME) = $61.20
Let's see we just went down from $325.72 (68% MSIE) to $305.92 (51% MSIE + 17% OTHER) by only swapping 17% of the visitors to a lower CTR demographic.
Why has $19.98 vanished by browser attrition?
There are obviously a lot more things going on in AdSense that effect earnings but that's not the topic, assuming all things are equal and those clicks would pay the same either way, you're going to lose money.