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Nielsen Points To System ‘Flaw’ For Under-Reporting Time Spent On Websites

Nielsen has uncovered a glitch in its system that led it to under-report the amount of time users spent on websites and is investigating the issues, the company said in a client letter (pdf) obtained by AdAge. While it doesn’t appear that data related to counting website traffic was affected, Nielsen said it is continuing to investigate the cause of issue.

Specifically, Nielsen said the problems were found in the NetView service, which measures time spent on websites. The full effect on VideoCensus, MegaView Retail, MegaView Search, AdRelevance, WebRF services and custom research in those areas wasn’t entirely clear yet.

The under-counting was discovered when Nielsen execs noticed declines in time spent that they couldn’t explain. Eventually, Nielsen realized that the meters weren’t capturing all the usage data from sessions because of the long URLs in many social media sites, which in most cases are over 2,000 bytes each. That length would cause the processing to “time out,” resulting in average decline of 22 percent in time-spent year-over-year.

Nielsen says it will have new meters installed by December which should fix this particular problem. It has also asked the Media Ratings Council to review its findings.

The company has been working to build up its online metrics over the past year. In October 2009, Steve Hasker was hired from McKinsey & Co. as the audience measurement company’s president for media product leadership & advertiser solutions. This summer, Google (NSDQ: GOOG) product manager Ari Paparo left the search giant to become Nielsen’s EVP, online products.

While numbers of unique visitors is considered the most important number for websites, measuring time spent is becoming just as important for attracting advertisers, as promises of “engagement” are expected to yield more lucrative branding campaign dollars.