How ad format change doubled the CTR and revenue

About a week ago I received an email from Google AFMA (AdSense For Mobile Applications) about change of format of AdSense text ads for Android. Instead of fully clickable ad they added dedicated button on the right side of the ad with the rest of the ad unclickable. This was introduced as a step that should improve user experience (avoiding random clicks?) but possibly decreasing CTR (click-through rate). This is how ads appeared in my application APNdroid before and now:

What happened to CTR of APNdroid? It's doubled! It is just 8 days since the change, but I think it must be the button that makes the difference. I don't think it is content. It is just more asking for the click somehow. I can't stop wondering what a huge impact can such a subtle UI change have on the user behavior. Look at the stats from a little bit more that 2 months of ads serving in APNdroid. Unfortunately I can't share the numbers, but I can tell you a little secret :-)