Citing data that comScore released after the market closed on Wednesday, analysts said growth in Google's click-through rate has nearly ground to a halt.

Google's stock closed down US$14.11 (S$19.50), or 3.1 per cent, to US$444.08 in afternoon trading.

The click-through rate grew 3 per cent in February compared to a year earlier, and January saw no increase compared to January 2007.

Several months earlier, the rate was growing 25 per cent to 40 per cent compared to a year earlier. The new data is in line with click-through declines Google reported last quarter.

Google, which gets paid when users click on a sponsored ad that comes up as the result of a Google search, has reported steadily rising per-click revenue.

The Mountain View-based company said in January that the drop in click-through rates is a result of its efforts to boost the usefulness of each click to its advertisers' sales performance. For instance, the company decreased the space around a word that would result in a click, so more clicks would be intentional.

Analysts disagree on how long it will take Google's per-click revenue to adjust to any increased value per click it has created.

Mr Rob Sanderson, an analyst with American Technology Research, said per-click revenue will rise immediately if advertisers see more value in each click, because they'll pay more for them at auction.

'It's not clicks that advertisers are really buying, it's what those clicks get them, which is sales conversions,' said Mr Sanderson.

Mr Colin Gillis, an Internet analyst at Canaccord Adams, also was optimistic.

'It's very difficult to spin this as positive data point, but it also doesn't mean the world is ending,' Gillis said.

The click-through rate is only one piece of the equation for Google, he said.

'The counter point is that Google is out there saying, 'We are trying to make our clicks more worthwhile.' They want to actually deliver relevant hot leads to their customers because that's what their customers want,' Mr Gillis said.

Other analysts disagreed.

Piper Jaffray analyst Gene Munster predicted Google will fall short of Wall Street expectations in the current quarter because of the click-through rate.

Lehman Brothers analyst Doug Anmuth cut his 2008 profit estimate for Google and reduced his price target to US$580 per share from US$644, citing the click-through rates.

He also said advertisers may be trimming their budgets - and not responding to the changes Google has made.

Google, which reports first quarter earnings April 17, declined to comment on the comScore data.

Numbers from comScore are closely watched by some industry analysts, even though the firm uses online recruitment techniques dismissed by many traditional pollsters.

Mr Sanderson said comScore's numbers have a wide margin of error and can't be used to predict quarterly results.

'ComScore data has a really wide range of plus or minus in terms of being accurate. They don't know what the real number is, it's just a sample,' he said. -- AP