NEW YORK—The Media Ratings Council, which accredits audience measurement services, has issued a statement flagging potential problems with Nielsen’s National Big Data + Panel Television measurement service. The group also described how it is working with Nielsen to resolve those problems, which resulted in notable declines in viewing among people aged 25-54 in the first half of 2025.
During the first half of 2025, MRC said that it became aware, through various sources, including its own ongoing audit-related work, “of seemingly unusual changes in measurement results from the Service; for example, decreases in audiences for certain demographics (e.g., total day impressions for persons 25-54 years old declined by more than 10% on average during the first half of 2025, as compared to the first half of 2024).”
It also flagged “issues with representation levels in Nielsen’s panel (household viewing technology as well as demographic characteristics), as well as changes in the general variability associated with reported audience estimates and between audience estimates originating from Panel only vs. Big Data + Panel measurements.”
Nielsen’s National Big Data + Panel Television measurement service has been accredited by the Media Rating Council (MRC) since January 2025 and remains accredited.
The MRC noted that the service involves a "complex set of measurement processes that rely on several data sources such as Return Path Data from set-top boxes, Automated Content Recognition Data from certain smart television brands, Streaming Data (both from the Nielsen National audience measurement panel for general streaming activity and integrations with 3rd party sources for certain live sports events) and Nielsen’s National television audience measurement panel distributed across the United States."
The Nielsen service also relies on certain machine learning algorithms and techniques (i.e., “modeling”) to derive audience estimates, including certain procedures to predict demographic information associated with non-panel sourced tuning information.
To maintain that accreditation, the MRC said that it had “identified four priority areas that we believed required Nielsen’s actions to help address the issues: 1) Implementation of an independent media-related universe estimate source, 2) Changes to Nielsen’s modeling processes to increase demographic assignment accuracy, 3) Changes to Nielsen’s weighting process to help simplify the overall process and reduce standard error levels in reporting, and 4) Improving underrepresented demographic segments in Nielsen’s panel (e.g., Hispanic, Spanish Dominant).”
“In September 2025, MRC informed Nielsen that improvements on these four matters was necessary to maintain accreditation of the Service,” the group said.
Since that time, Nielsen has conducted and shared research as well as proposed several solutions to address these areas, the MRC reported.
In February 2026, Nielsen implemented the ARF DASH study as a source of media-related universe estimates. It should also be noted that the ARF DASH study was granted MRC accreditation in early 2026 after successfully completing a separate MRC audit process.
The MRC also said that in terms of underrepresented demographic segments, Nielsen made notable progress in quarters three and four 2025 and into January 2026, and has expressed a commitment to continue focusing on balancing demographic representation since we believe further work is needed in this area.
In addition, the MRC reported that adjustments to Nielsen’s modeling and weighting processes are currently planned for implementation in April 2026.
“At present, MRC members are awaiting impact data for these changes on a combined basis to better understand the nature of the changes as well as to verify expected reduction in bias and in statistical variability,” the group said. “Impact data is currently being delivered by Nielsen in phases to enable our evaluation and provide notice of impacts to the marketplace.”
The MRC also stressed that “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. We will continue to evaluate the estimated impacts of these planned methodological changes, with urgency, as they are important to Nielsen’s current accreditation of the commerce significant National service, which continues to be under evaluation at this time. Should the expected timing be modified or delayed, MRC will determine next steps on how to proceed.”
