When Nielsen notices one panelist obsessively listening to one station, either for one ratings period or book after book, does it drop that person from the panel? Or are such listeners treated the same way typical listeners are, and rotated out when their time comes? How about when two or three people exhibit the same listening behavior? Does Nielsen kick them out for suspected funny business?
Nielsen Audio does have an "Outlier Mitigation" policy, outlined in this document on page 8-3. Note that the outlier remains in the panel, but has its listening reduced as described:
Local Radio Syndicated Services Description of Methodology
"In some cases, a station may have an unusual increase in the ratings based on a single Panelist or home with very heavy listening. We call these situations “Outliers.”
For the purpose of our Outlier Mitigation methodology, we define an outlier as a Panelist that accounts for 50% or
more of the station’s total listening within the Metro, that ranks in the 99.5 th percentile of the Metro’s listeners,
and that exhibits no security risk. With Outlier Mitigation, panelists identified as Outliers will remain in the Panel,
but tuning that exceeds the specified threshold will be trimmed to the level of the next heaviest listener to the
station outside of the household...."
So, at least there, I don't see anything that specifically addresses the kind of multi-panelist "collusion" you ask about. I would think that a station suspecting something like that could bring it to Nielsen's attention.
This article from Barrett Media takes a somewhat deeper dive:
Last week, this column explained sampling error. It’s a Survey 101 concept, but rarely considered in the world of ratings. This week, we’ll go through
barrettmedia.com
