Nielsen has admitted that there were inadequate checks and balances in place to correct a logging error which could have affected the data around nearly a quarter of a million TV ads.
The gaffe, confirmed to AdNews this morning, affected TV ads on two free-to-air networks during the first five months of the year.
It said there was a time stamp error in its spot monitoring data, affecting the data given to media buyers and clients on how many people ads reached.
Nielsen monitors the times ads run on free-to-air TV, which is then matched with OzTAM data to give buyers data on just how many people were watching ads at any particular time.
It is believed that the logs taken by a few Nielsen machines ran a few minutes slow, meaning data for any particular spot measured by the affected machines was wrong.
It said that the error affected 1% of the circa 25 million TV spots it monitored during the time.
Nielsen is currently undertaking an incident report to get a handle on the damage, but a spokesperson said there were few checks and balances in place on the spot checks meaning the problem went on for the five months without being detected.
However, they added that additional spot-checks were in place now.
It is believed the data error is contained to the first five months of the year, with Nielsen saying that it had confidence that this error had not occurred before the five-month window despite the inadequate oversight employed.
The data errors threaten to waver confidence in Nielsen, and comes after it signed an extension with IAB Australia for digital measurement.
IAB said its confidence in Nielsen was unshaken by this morning's revelations, with its contract including several data-measurement and verification measures.
“IAB Australia has built a range of KPIs and monitoring systems into the digital audience measurement deed with Nielsen. The data and systems will be reviewed in detail each month by the IAB’s Measurement Council,” IAB CEO Alice Manners told AdNews.
It also comes after Nielsen's US arm admitted in October that data errors dating back to March meant the autumn TV ratings data was incorrect. However it believed there too that the errors were small.
Nielsen is set to meet with the Media Federation Australia this afternoon to update the industry body on how widespread the issue is and how the problem could have affected the media industry.
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