I can't recall if Nielsen ever ran a commercial, but it just dropped an "explainer video" promoting why its new Big Data + Panel is a "new-and-improved" advertising currency.

This article studies non-parametric panel data models with multidimensional, unobserved individual effects when the number of time periods is fixed. I focus on models where the unobservables have a ...

We propose a varying-coefficient panel-data model with unobservable multiple interactive fixed effects that are correlated with the regressors. We approximate each coefficient function using B-splines ...