Posted by Dr-Pete For the past couple of months, Google has been testing SERPs with 4 ads at the top of the page (previously, the top ad block had 1-3 ads), leading to a ton of speculation in the PPC community. Across the MozCast data set, 4 ads accounted for only about 1% of SERPs with top ads (which matches testing protocol, historically). Then, as of yesterday, this happened: Over the past 2 weeks, we’ve seen a gradual increase, but on the morning of February 18, the percentage of top ads blocks displaying 4 ads jumped to 18.9% (it’s 19.3% as of this morning). Of the 5,986 page-1 SERPs in our tracking data that displayed top ads this morning, here’s how the ad count currently breaks down: As you can see, 4-ad blocks have overtaken 2-ad blocks and now account for almost one-fifth of all top ad blocks. Keep in mind that this situation is highly dynamic and will continue to change over time. At the 19% level, though, it’s unlikely that this is still in testing. Sample SERPs &...