Click-through ad effectiveness questioned

For some time, I've wondered about the effectiveness of online advertising. Supporters have always said, "Look at click-through rates." A major study, reported by MediaPost, says those rates are virtually worthless. According to MediaPost, "99% of stable cookies examined by ad network and technology provider Collective Media show no evidence of clicks." And, it says, when they do show up, there's little evidence of actually purchasing anything. That's my experience. I have inadvertently clicked on ads, but never used them to buy anything. If I were an advertiser, I'd be looking carefully at how effective my ads are.