Targeting efficiency
Despite what Google might tell you, its targeting efficiency is not all that great. Since we have no reliable way to test this at a network level, here are a few examples. I found an ad for a JCPenney ”Back to School Sale” on a blog about Taiwan. JCPenney has stores in the U.S. and Puerto Rico only.
Here is another example of poor targeting efficiency. A site where a doctor blogs is being targeted by blog providers rather than medical providers.
What determines this is the equilibrium between content and advertising. If the supply of ad slots (i.e., content spaces) are sufficiently high, then targeting efficiency will be high. If the keyword of choice does not map well with the available content, it will be shunted off to a site that is a poor fit.
The bottom line is that Google's AdSense targeting efficiency is still not very high.
Grade: B