U.S. programmatic digital out-of-home advertising spend will more than double in 2020 year over year, totaling $181.6 million, rising to $533.8 million by 2022, according to eMarketer's forecast. The estimate puts programmatic DOOH accounting for 2.2% of total OOH ad spending in the U.S. in 2020. A OOH campaign can be set so inventory is programmatically purchased whenever certain conditions are met. eMarketer explains.