A WebmasterWorld thread started by moderator martinibuster has been getting a lot of attention over the weekend. MartiniBuster asks other members to come up with theories on why it appears AdSense earnings are lower these days then a year prior.

MartiniBuster’s own theory is pretty interesting. In short, he says that there are less AdWords coupons floating around these days, so less people are experimenting with the content network. Let me quote MartiniBuster:

Now, there are many other theories for the lower earnings, outside of the world being in a recession. They include:

Google needs to take a bigger piece of the AdSense pie
Slow down in new fresh to the net ad clicking users.
Ad blindness for veteran net surfers.
Less MFA has to affect a segment of publishers.
Landing page rules turning off some advertisers.
AdWords complexity
Google dropping the ball on code quality due to lack of competition for too many years leading to data loss that is later artificially unfairly balanced out.
More advertiser control positively affecting few and devastating the rest.
Google silently taking a bigger portion of publisher’s earnings to meet the market expectations.
Smarter advertisers
Over saturation of content

There are many more ideas and theories being debated in the thread.

Forum discussion at WebmasterWorld.