By: Anick Jesdanun, AP Internet Writer
(AP) A leading Internet traffic-measuring service says it underestimated workplace Web site audiences by several million visitors and is reissuing numbers for a three-month period.
ComScore Media Metrix sought Monday to portray the revisions as an improvement rather than a correction. But ComScore’s main rival, Nielsen//NetRatings, said the change was more extensive than anyone in the business had done.
Such Internet traffic measurements are used, among other things, by advertisers in deciding where to place their ads and by Web sites for bragging rights. News organizations also cite the numbers.
The extent of ComScore’s revisions varied.
For instance, AOL Time Warner sites saw traffic for December adjusted to 111 million unique U.S. visitors, an increase of 3% from 108 million. Google’s numbers became 49 million, a 14% jump from 43 million.
WeatherBug also lost bragging rights to what one press release described as “the number one source for weather information on the Web.” Instead, the honor returns to rival Weather.com.
The changes affect ComScore’s Media Metrix 2.0 service, which measures U.S. audiences. Global and e-commerce ratings were done separately and did not require changes.
ComScore’s revisions for October to December stemmed from changes in how the company estimates Internet use at the workplace. Such services often have trouble getting enough employers to agree to participate, so ComScore had devised a formula to estimate the undercount.
ComScore started using a new methodology last fall following its acquisition of Media Metrix from what is now Jupiter Research. After a few months, ComScore decided to make some adjustments.
Peter Daboll, president of ComScore Media Metrix, said ComScore could have used the adjusted methodology “on a forward basis” only but decided to also adjust past numbers to permit comparisons.
Sean Kaldor, vice president of marketing at NetRatings Inc., acknowledged that his company had occasionally adjusted numbers and methods in the past — but nothing fundamental enough to affect multiple months of data.
In acknowledging the underreporting by restating numbers, Daboll said, ComScore was purposely accepting “short-term pain for long-term gain.”
Nielsen//NetRatings is a joint service of VNU-owned Nielsen and NetRatings, which is majority-owned by VNU, the parent company of E&P.