1

We obtain most of our data on advertising during the 2016 campaigns from the Wesleyan Media Project (WMP), which is a collaboration of researchers at Wesleyan University, Bowdoin College, and Washington State University. The project, which started tracking political advertising 2010, is a successor to the Wisconsin Advertising Project, which tracked political advertising back to 1998. WMP data come from a commercial firm, Kantar Media/CMAG, which tracks the placement of ads on broadcast television in all 210 media markets in the United States. From these data, we can know the station on which each ad aired, the time it aired, its length, and an estimate of its cost. WMP staff then analyzes video of each unique ad, coding it on over 50 different characteristics, including the tone of the ad, whether it is primarily about policy or candidate characteristics and the specific issues mentioned. Intercoder reliability checks on coding found 97 percent agreement between independent assessments of tone for a Kappa score of 0.95 and 83 percent agreement between independent assessments of the personal/policy variable for a Kappa score of 0.76. Because Kantar/CMAG data do not provide information on local cable advertising, we supplement these data with information obtained from NCC Media, which both sells and tracks advertising on local cable television across the US.