MRC Blows Whistle On Nielsen Big Data

MRC Blows Whistle on Nielsen Big Data + Snafu by 

Joe Mandese , 

Yesterday Industry ratings watchdog the Media Rating Council (MR) this week disclosed major problems in Nielsen's Big Data + panel measurement service that have caused "seemingly unusual changes" in its audience estimates, including a double-digit decline in adults 25-54 viewing, as well as other issues. In a statement published on its website Tuesday the MRC said it became aware of the issues during the first half of 2025 from undisclosed sources, as well as part of its ongoing auditing of Nielsen's service and described the unusual changes as: Decreases in audiences for certain demographics, including an average 10% decline in total day impressions for persons 25-54 vs. the same period a year earlier. Issues with representation levels in Nielsen’s panel, including household viewing technology, as well as demographic characteristics. Changes in the general variability associated with reported audience estimates and between audience estimates originating from panel-only vs. Big Data + panel measurements. advertisement BISRetail-sp26-InsiderCircle-640x480dbl.gif advertisement In its statement, the MRC did not explain why it is disclosing the problems now, but it said that it informed Nielsen in September 2025 that it needed to do four things in order to maintain MRC accreditation for the service: Implementation of an independent media-related universe estimate source. Changes to Nielsen’s modeling processes to increase demographic assignment accuracy. Changes to Nielsen’s weighting process to help simplify the overall process and reduce standard error levels in reporting. Improving underrepresented demographic segments in Nielsen’s panel (e.g., Hispanic, Spanish-dominant). Regarding the first area, the MRC noted that Nielsen began implementing the Advertising Research Foundation's DASH (Universe Study of Device & Account Sharing) service, which the MRC previously accredited and which is increasingly becoming an industry default standard for media universe estimates. Regarding under-represented demographic segments, the MRC characterized Nielsen as making "notable progress in quarters three and four 2025 and into January 2026," and disclosed that Nielsen will make "adjustments" to its modeling and weighting processes beginning in April. The timing of those changes could be disruptive for the advertising marketplace heading into 2026-27 upfront negotiations, in which Nielsen still remains the default currency, though a number of alternative currencies are also being implemented by buyers and sellers. "We understand and we regret that these changes will be disruptive to business processes of the marketplace; we are encouraged that Nielsen is actively working to address the priority areas for improvement that have arisen in their Big Data + Panel measurement.," the MRC stated, adding that the Nielsen service remains accredited for now, but is "under evaluation at this time."