Advertiser investment in private marketplaces (PMPs) has risen over the past several years thanks to ongoing issues of ad quality and brand safety associated with open market buying. Next year, for the first time, US ad spending on real-time bidding (RTB) transactions where buyers and sellers have some sort of private agreement in place will overtake outlays on open exchanges, per our latest forecast.

We estimate US advertisers will spend $12.22 billion on open exchanges and $11.56 billion on PMPs this year. By 2021, those figures will rise to $13.77 billion and $15.97 billion, respectively.

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