What is of interest is does that 8% comprise of the same people? Or does it change?

When Michael Dell was young and selling newspaper subscription, he found that only 2 kinds of people bought newspaper subscriptions. Those who just got married. Or those who just shifted homes. Out of the total population, maybe 5% fit this criteria. But the people who form this 5% change constantly. (I don't know if its 5% or 7% or 10% - pulled it out of thin air to make a point.)

So if the % of clickers fluctuates or even goes down, but the people who form the clickers group keep on changing, then online advertising makes a lot of sense.