Pubmatic released a report covering the massive drop– Q408 average CPMs are at 26 cents.  Before folks claim economic peril, let’s consider a few other factors.  The mix of inventory for ad network has shifted dramatically to social, which has historically terrible CPMs.  From a weighted average perspective, it’s hard to say exactly the impact, but we know that 4 of the top 10 sites out there are now social and that social traffic recently passed adult as the largest category.  And the reason that social network have bad traffic is not necessarily because of a young demographic.  The more pages that users consume on a site, the lower the frequency they click on ads.   If heavy users are consuming 60 to 100 pages per day on a social network, as opposed to 6 to 10 pages on other sites, you cannot expect ad clicks to increase in linear proportion to pageviews.

What I’d like to see is gross earnings by site quarter over quarter.   Internet advertising is such that we have a growing audience of users consuming more pages per session– thus CTR will continue to slide.  And if revenue per click is constant, you can’t help but see eCPM (what publishers are earning per thousand impression) and CPMs slide.  My hunch is that gross earnings per site are flat, as opposed to down 50%.  Falling CPMs is both normal and good.