Okay, firstly -- there is no Google AdMob forum so I figured this would be the best place to post this.
On Google AdMob you can advertise your APP in other people's APPs. I created the text banner. It is called "Pickles Maths Game for Kids". That's it. That's the exact text displaying. An unmistakable description.
So, after 5000 clicks split evenly between the two platforms, I have had 2 downloads on iTunes and 9 downloads of the Android version. I only targeted users in the UK and the US.
That is a 0.22% conversion rate on an app that is FREE.
So, is Google AdMob simply packed with fraudulent publishers? Or did the other 4,989 people that clicked on my ad for a 'Maths Game for Children' get to my APP download page and think "wait a minute! I don't want to download a free maths game for children after all. what was I thinking?"
And sorry, I should have put up some comparisons. Facebook advertising is always poor for us. But even Facebook ads result in at least 1 download per 50 clicks. We ran that campaign before the AdMob one but stopped it because 1 in 50 clicks is bad ROI.