A WebmasterWorld thread is at the beginning of people sharing their ICR, invalid click rates, reported by Google since they released "Invalid Clicks" in AdWords Reports.
One Google AdWords advertiser shares;
In my case ICR's have tended to fluctuate between 5.5% and 9.0%, for campaigns where content bids are ~1/5th search bids and still accounting for ~40% of total clicks.
An other advertiser shares;
Depending on the global region, I'm anywhere from 2.5% to 7.5%... the US is near the low end of the range, Asian countries at the high end.
What is your ICR? And more importantly, do you think it is accurate? Forum discussion at WebmasterWorld.