Nielsen: We Missed 5% Of Users For The Top 1,000 Sites

Nielsen underreported the audiences of the top 1,000 Web sites by an average of 5% during the month of September, due to a previously disclosed glitch in its measurement system that caused it to miss Web sites with long URLs, or domain names. Nielsen did not disclose what the impact was on specific Web sites, but said that social gaming Web sites were impacted more than other Web site categories, according to its analysis of the situation.

In a communiqué sent to clients today, Nielsen said the glitch primarily affected online audience estimates for its NetView service, and that the impact was "significantly less" on its VideoCensus service.

Nielsen said it has begun final testing of a "solution" that would increase the "incidence of very long URLs," and that it plans to make that change effective with its December audience measurement and that it would also apply it retroactively to the data it reports for November. "We are delaying the delivery of November data until the end of December to ensure these changes are incorporated in our next data release," Nielsen said in the client notice.

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