clipped from www.economist.com

The case of the missing clicks

What does it mean when people click on Google's ads less often?

The scare started when comScore, a research firm, reported in late February that Google's “paid clicks” had decreased by 7% during January, and were flat compared with the same month a year earlier.

the ratio of paid clicks to searches dropped even faster than the number of paid clicks: it was down by 16% in the month of January.

eMarketer, another research firm, projects that online advertising in America will grow by 23% this year, economic troubles notwithstanding, because the measurability of the medium is too compelling for marketers to ignore.

the likeliest explanation is instead that Google itself is to blame—by, paradoxically, increasing the quality of its ads

this is what drove Google's revenue last year: it grew by 56% on the back of a 21% increase in revenue per paid click.