Thing is, one wonders what percentage of the total vote is informed and motivated by hoardings alone. It's a scary thought, given they tell us little other than candidates' self-promotion skills and ability to pull together a kingsize selfie.
What's also intriguing is the product placement. That is, billboard sites can often give away more than the billboard itself - not to mention betray the political colours and collusions of the hoardings' landlords.
Some erect signs on free-standing frames, some are fixed to stacks of apple bins, in residential backyards, pastoral sites and atop scrap metal dealers. Don't assume this is inconsequential. There's a subtext to their physical presence which invites a closer reading.
In terms of billboards, think not just what you read, but where you read.