“…I have not discussed other practical issues related to big data and nonprobability samples, such as privacy, access and transparency, and I refer the reader to the following overview and appraisal papers: Baker et al (2013), Brick (2011), Citro (2014, Couper (2013), Elliott and Valliant (2017), Groves (2011), Kalton (2019) , Keiding and Louis (2016), Lohr and Raghunathan (2017), Mercer et al (2017), Tam and and Thompson (2019). The report by the National Academies of Sciences, Engineering, and Medicine (2017) extensively treated the privacy issue, in addition to methodology for integrating data from multiple sources.…”