Nielsen is acknowledging that it under-counting out-of-home audiences since September 2020, in the latest blow to a company that lost Media Rating Council accreditation for its larger national and local TV ratings services earlier this year. 

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“As part of routine testing and quality controls, we recently identified an error that caused an understatement of reported out-of-home audiences for our national TV service,” Nielsen said in a statement. “While there is no impact to most telecasts, and no impact to local television, we did find some variances for events that tend to yield larger out-of-home audiences, such as live sporting events. The error has been corrected, and Nielsen will be reissuing data from September 2020 to present in order to provide the industry with the most complete data.”

Counting live sporting events is the most crucial element of out-of-home measurement, as TV networks long have contended they don’t get proper credit for large live sports audiences in restaurants and bars. Nielsen’s out-of-home measurement was a bone of contention at its launch, as the company reversed a decision to delay rollout of the measurement amid the pandemic after pushback from TV networks.

The latest counting errors couldn’t come at a worse time for Nielsen; its TV ratings MRC accreditation was suspended in September over similar under-counting issues across the much bigger in-home TV market. The company is looking to restore faith in its accuracy among the marketers, agencies and media companies that will decide whether to re-instate that accreditation or grant accreditation for its new Nielsen One cross-platform measurement service.

Nielsen announced earlier this week that it's given 10 agencies and media companies access try out a Nielsen One Alpha version of the next-generation measurement in advance of an expected December 2022 full launch.

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The Video Advertising Bureau, a media trade group that sharply critcized Nielsen and pushed for suspension of its accreditation earlier this year, lashed out at the company anew.

“Today’s announcement by Nielsen of more systemic errors that have further undercounted TV ratings for the last 16 months is unfathomable, both for Nielsen and the buyers and sellers that use Nielsen data as trading currency,” said VAB CEO Sean Cunningham in a statement. “While the VAB and our Measurement Innovation Task Force have been looking to build back confidence in Nielsen’s core measurement capabilities, the timing of this latest and stunning omission of OOH viewership not being counted across the growing broadband-only home universe coincides with our recent discovery of significant defects in Nielsen’s overall plans to include broadband-only homes in early 2022 for local TV. Given the unprecedented scale of Nielsen’s 2021 undercounting and the depths of discovered defects in their core competency on TV measurement, we are greatly concerned that Nielsen One is being built atop a broken and defective measurement and currency foundation.”