Taxes and the environment followed as the third- and fourth most-mentioned, respectively.
The entire report is worth reading (looking at you, political nerds) but what is perhaps most surprising is the sudden drop of international affairs from the top 15 list. Ads related to terrorism have been a steady presence on air since Islamic State militants began making headlines over the summer. Those spots have also had an outsized presence online, where they have received widespread attention owing to their often-controversial imagery.
The authors of the report include an important qualifier on their findings: While the information they've compiled looks at spot counts in absolute numbers, it does not account for overall impressions or the potential viewership of each ad.