Here is the answer to your question from Jeff Dickey, Founder/VP Business Development, SeeSaw Networks:

“While standards have yet to be agreed upon, one emerging currency for digital signage buys is CPM, where the impressions are determined using the combination of a validated traffic number multiplied by an awareness
number. This formula truly brings an apples-to-apples comparison to digital out-of-home media buys that span multiple digital out of home networks.

National advertisers are reluctant to buy on flat rates simply because not all locations are equal, even within the same network (different demos, different traffic, etc.). Some networks have gotten away with requiring nationwide/network-wide buys, but those days are numbered as the advertisers push toward more specific buys with greater and greater levels of targeting.

If the research is available to support the demographics of female, Hispanic, or age groups — even better if the demographic data can be day-parted — a premium can definitely be applied to the better opportunities the advertiser has to reach their target audience.”

Jeff Dickey, Founder/VP Business Development, SeeSaw Networks