A second approach to tracking spending on digital media in campaigns is to
rely on data collected by platform-independent media tracking ﬁrms. A typical
approach employed by these companies is to send web crawlers to the top
trafﬁcked websites each day, capturing the volume of advertising from
various sponsors and estimating the sponsor’s spending, based on the number
of ads identiﬁed. Ridout et al. (2017, 2018) used data from a ﬁrm called
Pathmatics to report on spending in the 2016 presidential race – and to
identify when various sponsors deployed advertisements online. Pathmatics
estimated at least $58 million in spending on digital in the 2016 presidential
campaign, but this is admittedly a severe underestimate because the ﬁrm at the
time did not track spending on social media and, most importantly, on
Facebook. On average, candidates in Senate races spent 11.4 percent of their
ad budgets on Google and Facebook, while candidates in competitive House
Social_Media_and_Democracy