Forbes ran ad effectiveness research with Dynamic Logic and repeatedly saw a slightly older composition of survey respondents in that research than what they were seeing in Comscore Unique Visitor data for their property.
Diagnosed the skew towards older web visitors among high pageview (and therefore ad) consumption as well as the fundamental media planning issue of using UV composition versus PV composition. I created the white paper and summary (below) and presented it to Forbes.
Why this issue is significant:
The demographic disparities we see here are the same as what we see in current day (2016) audience verification studies. Nielsen OCR and Comscore VCE often show older audiences being reached compared to the Unique Visitor data viewed during the planning process.